RKI H361818 36 x 18 Alternatives: 6 Similar Picks Compared
As an Amazon Associate we earn from qualifying purchases. Links on this page are affiliate links.
The RKI H361818 36 x 18 alternatives list helps you find similar storage solutions if this steel underbody box does not fit your needs. This original unit measures 36 x 18 x 18 inches and weighs 87 pounds, offering heavy-duty protection for trucks or SUVs. Its steel construction provides durability, but the significant weight and specific underbody design limit its use for general rooftop cargo. You might need a lighter option or a different mounting style for your vehicle. These alternatives were chosen because their specifications overlap with the original product, ensuring comparable dimensions or utility. The list includes seven other picks ranked by their specific strengths, such as premium weather resistance or budget-friendly capacity. Each item shares key traits with the RKI box, such as size constraints or material quality, while addressing different use cases. Whether you need dual-side opening access or a slim profile for smaller roof racks, these options provide viable replacements. Review the specs to see which model matches your vehicle's roof rack width and your cargo volume requirements. This guide compares the data to help you select the right carrier without guessing.
Our top pick: RKI 36x18x18 Steel Underbody Box.
How alternatives compare to RKI
Pelican BX140R Cargo Case
The Pelican BX140R Cargo Case shifts from underbody mounting to roof rack use, requiring a separate mount. It measures 46 x 24 x 11.5 inches and weighs just 35.1 pounds, making it significantly lighter than the 87-pound RKI steel box. This case prioritizes rugged, weatherproof protection for valuable gear over sheer volume. You gain portability and durability but lose the heavy-duty, fixed underbody security. Choose this if you need a lightweight, premium case for roof racks or truck beds rather than a permanent under-vehicle storage solution.
GarveeTech 14 cu ft Dual-Side Opening Roof Box
The GarveeTech 14 cu ft box offers dual-side opening access, a feature the RKI underbody unit does not provide. Measuring 62.2 x 31.5 x 13.4 inches, it is much longer and wider but sits lower at 13.4 inches high. Weighing 44.8 pounds, it is lighter than the RKI’s 87 pounds. This ABS roof box prioritizes easy access and budget value over the heavy-duty steel construction of the RKI. Pick this alternative if you need large, accessible storage on a roof rack and prefer a lighter, more versatile option for general travel.
Eylar SRX-175 Overlanding Cargo Case
The Eylar SRX-175 Overlanding Cargo Case is a lockable, waterproof hard case designed for truck-bed or roof-rack overlanding. It measures 47.2 x 18.4 x 13.2 inches with a 175L capacity. Unlike the RKI’s steel build, this case focuses on rugged, secure storage for outdoor adventures. It lacks a listed weight, but its design targets overlanding use rather than general underbody storage. Choose this if you need a lockable, weather-resistant case for rugged terrain. It trades the RKI’s heavy-duty steel durability for specialized overlanding security and fitment.
DNA Motoring 13 cu ft Hard Shell Roof Box
The DNA Motoring 13 cu ft Hard Shell Roof Box provides a 110 lb load capacity and dual-side opening. Measuring 56.3 x 36.8 x 16.3 inches, it is longer than the RKI but offers roof-mounted convenience. Its ABS shell is lighter and more aerodynamic than the RKI’s 87-pound steel box. This option is ideal for buyers needing a practical, lockable roof box with good capacity. Pick this if you prefer a lighter, weatherproof roof solution with easy access over the heavy, fixed underbody storage of the RKI steel unit.
Relaxcabine 15.5 Cu Ft Dual-Open Roof Box
The Relaxcabine 15.5 Cu Ft Dual-Open Roof Box features dual-side opening for easy access, unlike the RKI’s fixed underbody design. It measures 58.3 x 35.4 x 13 inches and weighs 34.3 pounds, making it much lighter than the 87-pound steel RKI box. This hard shell, lockable case prioritizes quick loading and family use over heavy-duty durability. Choose this alternative if you need a lightweight, accessible roof box for frequent loading. It trades the RKI’s robust steel construction for convenience and ease of use on roof racks.
Menabo Mania 320 Liter Roof Box
The Menabo Mania 320 Liter Roof Box is a slim, compact option measuring 55 x 14.3 x 31.5 inches. It weighs only 19.8 pounds, significantly lighter than the RKI’s 87 pounds. This 11 cubic foot box is designed for standard roof racks, offering a secure, quick-install profile. Unlike the heavy steel RKI, this ABS case prioritizes aerodynamics and low weight. Pick this if you need a lightweight, compact roof box for moderate cargo needs. It offers easier handling and installation compared to the heavy, fixed underbody RKI steel box.
Quick picks
Our 7 picks
RKI 36x18x18 Steel Underbody Box
Best for: heavy-duty underbody storage on trucks or SUVs
- Dimensions
- 36 x 18 x 18 in
- Material
- Steel
- Weight
- 87 pounds
The RKI H361818 is a 36 x 18 x 18 inch steel underbody cargo box designed for secure, lockable storage underneath a vehicle. Weighing 87 pounds, it is built from heavy-duty steel and offers a compact, low-profile shape. This box suits those who need a rugged, permanent storage solution for tools or gear.
Pros
- Steel construction for maximum durability and security
- Compact 36 x 18 x 18 inch size fits under many vehicles
- 87-pound weight indicates heavy-gauge material
Cons
- No dimensions for interior capacity or usable space listed
- Heavy steel design may require two people to install
- No mounting hardware or installation instructions included in specs
Good fit if
- You need a rugged, lockable steel box for under-vehicle storage
- You have a truck or SUV with clearance for a 18-inch tall box
- You prioritize security and durability over lightweight convenience
Skip if
- You need a lightweight, easy-to-mount rooftop cargo box
- You require a box with a larger capacity or taller profile
- You prefer a plastic or composite material for lower weight
Verdict: RKI 36x18x18 Steel Underbody Box is a heavy-duty steel underbody box for those who need secure, compact storage underneath a vehicle, but its weight and lack of listed interior capacity may limit its appeal for general rooftop cargo use.
Pelican BX140R Cargo Case
Best for: rugged, weatherproof gear storage on roof racks or trucks
- Water Resistance
- Weather resistant, dustproof
- Installation
- Cargo Roof Mount (sold separately)
- Dimensions
- 46 x 24 x 11.5 in
- Recommended Use
- Gear, clothing, tools, dry food
- Weight
- 35.1 pounds
The Pelican BX140R is a heavy-duty, weather-resistant cargo case designed for roof racks, truck beds, or SUV storage. Its exterior measures 46 x 24 x 11.5 inches with an interior volume of 41.75 x 19 x 8.75 inches, and it weighs 35.1 pounds empty. It suits you if you need extreme durability and dustproof protection for gear, clothing, tools, or dry food.
Pros
- Extreme durability and weather-resistant, dustproof construction
- Heavy-duty lay-flat handles and tie-down plates for secure transport
- Limited lifetime guarantee on the case
- Available in 8 size variations (different heights and models)
Cons
- Requires a separate Pelican Cargo Roof Mount for roof rack installation
- Interior depth of 8.75 inches limits taller items
- Empty weight of 35.1 lbs is heavier than many soft-shell alternatives
Good fit if
- You need a rugged, weatherproof case for valuable or sensitive gear
- You plan to mount the case on a roof rack, truck bed, or inside an SUV
- You value a brand with a limited lifetime guarantee
Skip if
- You want a roof box with a built-in mounting system included
- You need to carry tall items (over 8.75 inches interior height)
- You prefer a lightweight cargo carrier under 20 lbs
Verdict: Pelican BX140R Cargo Case is a premium, durable weather-resistant cargo case best for protecting valuable gear, but requires a separate roof mount and has limited interior height.
GarveeTech 14 cu ft Dual-Side Opening Roof Box
Best for: budget buyers needing large, dual-side storage
- Capacity
- 14 cu ft
- Shell Type
- ABS
- Opening
- dual-side
- Load Capacity
- 165 lbs
- Water Resistance
- waterproof
- Security
- 2 keys and 2 straps
View on Amazon: GarveeTech 14 cu ft Dual-Side Opening Roof Box
This GarveeTech rooftop cargo box gives you 14 cubic feet of storage in a 62.2-inch long, ABS hard shell. It opens from both sides for easy loading and holds up to 165 lbs. The waterproof, UV-resistant build suits budget-conscious travelers who need a large, universal-fit box for vehicles with a roof rack.
Pros
- Dual-side opening for access from either side of the vehicle
- 14 cu ft capacity with a 165 lb load limit
- Waterproof and UV-resistant ABS shell
- Includes 2 keys and 2 straps for security
- Aerodynamic shape to reduce fuel consumption and noise
Cons
- Weighs 44.8 lbs, heavier than some smaller boxes
- Only 13.4 inches tall, limiting bulky items
- No integrated locking mechanism beyond the included keys
Good fit if
- You want a large, budget-friendly cargo box with dual-side access
- You have a roof rack and need extra space for road trips
- You prefer a waterproof, UV-resistant hard shell
Skip if
- You need a taller box for bulky gear like camping chairs
- You want a lighter cargo carrier under 40 lbs
- Your vehicle lacks a roof rack or crossbars
Verdict: GarveeTech 62.2 in Dual-Side ABS Box offers a spacious 14 cu ft and dual-side opening at a budget-friendly price, making it a solid choice for travelers who prioritize access and value over height.
Eylar SRX-175 Overlanding Cargo Case
Best for: truck-bed or roof-rack overlanding storage
- Capacity
- 175L
- Shell Type
- rotomolded hard case
- Water Resistance
- 100% Waterproof
- Dimensions
- 47.2"L x 18.4"W x 17.9"H
- Vehicle Type
- Truck
- Recommended Use
- Camping
The Eylar SRX-175 is a rotomolded, 175L waterproof hard case built for truck beds and roof racks. It measures 47.2 by 18.4 by 17.9 inches externally and weighs 38.5 pounds. A rubber gasket makes it 100% waterproof, and the gas-strut lid stays open hands-free. It suits overlanders and campers who need rugged, lockable, organized storage.
Pros
- 100% waterproof seal with heavy-duty rubber gasket
- Gas-strut lid stays open for hands-free loading
- Lockable latches (padlock-compatible) for security
- Includes two removable organizer trays, a divider, and a cargo net
- Built-in drain plug doubles as an improvised cooler
Cons
- External dimensions may be too long for compact truck beds or smaller roof racks
- No remote or keyless locking mechanism listed
- Padlocks for the latches are sold separately
Good fit if
- You need a waterproof, lockable case for overlanding or camping gear
- You want a hands-free lid that stays open while you load
- You value internal organization with trays and a divider
Skip if
- You need a rooftop cargo box with aerodynamic shape for highway fuel economy
- You prefer a lighter, less bulky storage option for occasional use
- You require a case that fits under a tonneau cover or in a compact truck bed
Verdict: Eylar SRX-175 Overlanding Cargo Case is a rugged, waterproof, and lockable hard case with 175L capacity, ideal for truck-bed or roof-rack overlanding use, though its size and weight may limit fit on smaller vehicles.
DNA Motoring 13 cu ft Hard Shell Roof Box
Best for: buyers needing a 110 lb capacity roof box
- Capacity
- 13 Cubic Feet
- Shell Type
- Hard Shell, ABS
- Opening
- Double side
- Load Capacity
- 110 lbs
- Water Resistance
- Weatherproof
- Security
- Security locking system with keys
The DNA Motoring rooftop cargo box adds 13 cubic feet of weatherproof storage with a 110 lb capacity. It is a hard-shell ABS box that opens from both sides for easy loading. It fits vehicles with cross bars and requires no tools to install. This box suits you if you need a secure, lockable cargo carrier for bulky items up to 110 lbs.
Pros
- Double-side opening for convenient loading and unloading
- 110 lb maximum load capacity when evenly distributed
- Security locking system with keys protects your gear
- Weatherproof hard-shell ABS construction
- No tool assembly required for installation
Cons
- Fits only vehicles with cross bars, not all roof types
- At 16.25 inches tall, it may not fit under low garage openings
- No remote or keyless locking system listed
Good fit if
- You need up to 110 lbs of extra cargo space on your roof
- You want a box that opens from either side for easier access
- You prefer a tool-free installation that attaches to existing cross bars
Skip if
- You need a roof box that fits without cross bars
- You require more than 13 cubic feet of storage capacity
- You want a taller box for bulkier items over 16.25 inches high
Verdict: DNA Motoring 13 cu ft Hard Shell Roof Box offers a solid 110 lb capacity, dual-side opening, and weatherproof ABS shell at a practical size for vehicles with cross bars.
Relaxcabine 15.5 Cu Ft Dual-Open Roof Box
Best for: easy access and quick loading
- Capacity
- 15.5 cu ft
- Shell Type
- ABS and PMMA
- Opening
- dual-side
- Load Capacity
- 130 lbs
- Water Resistance
- weather-resistant
- Security
- built-in locking system
This Relaxcabine roof box offers 15.5 cubic feet of storage with dimensions of 58.3 x 35.4 x 13 inches. It features a dual-side opening design for convenient access from either side of your vehicle. The ABS and PMMA shell provides weather resistance, while the tool-free installation fits most crossbars. It supports up to 130 lbs of gear and includes a secure locking system. This model is well-suited for family trips and camping where easy loading is a priority.
Pros
- Dual-side opening for easy access
- 15.5 cubic feet of storage space
- Tool-free installation on most crossbars
- Secure built-in locking system
Cons
- 13-inch height is taller than aerodynamic low-profile options
- ABS and PMMA shell is less durable than aluminum
- 130 lbs load limit is lower than steel alternatives
Good fit if
- You need easy access from both sides of your car
- You are carrying bulky gear for camping or road trips
- You want a quick, tool-free setup on existing crossbars
Skip if
- You prioritize maximum aerodynamic efficiency and low wind noise
- You need to carry heavy loads exceeding 130 lbs
- You require a more durable aluminum construction for rough use
Verdict: Relaxcabine 15.5 Cu Ft Dual-Open Roof Box is a practical choice for families who value easy access and quick setup over maximum durability or aerodynamic performance.
Menabo Mania 320 Liter Roof Box
Best for: compact roof rack setups
- Capacity
- 320 liters/11 cubic feet
- Load Capacity
- 50 kg or 110 lbs
- Installation
- quick fixing system
- Vehicle Compatibility
- Compatible with all roof carriers
- Dimensions
- 55 x 14.3 x 31.5 in
- Weight
- 19.8 pounds
The Menabo Mania offers 11 cubic feet of storage in a glossy black shell. It measures 55 x 14.3 x 31.5 inches and weighs 19.8 pounds. The box features a patented double snap closure for security. It uses a quick fixing system for installation on any roof carrier. You can load up to 110 pounds into this carrier.
Pros
- 11 cubic feet of cargo space
- Patented double snap closure locks securely
- Quick fixing system fits all roof carriers
- Glossy black finish resists dirt
Cons
- 14.3 inches width limits side-by-side gear
- Single-side access only
- 110 pounds max load is moderate
Good fit if
- You need a compact box for weekend trips
- You have a standard roof rack system
- You prefer a low-profile black design
Skip if
- You require dual-side opening access
- You need to carry loads over 110 pounds
- You need a wider box for bulky items
Verdict: Menabo Mania 320L Roof Box fits drivers who prioritize a slim, secure profile for standard roof racks. It is ideal for those with moderate cargo needs who value a quick, universal installation.
Specifications side by side
| Spec | RKI 36x18x18 Steel Underbody Box | Pelican BX140R Cargo Case | GarveeTech 14 cu ft Dual-Side Opening Roof Box | Eylar SRX-175 Overlanding Cargo Case | DNA Motoring 13 cu ft Hard Shell Roof Box | Relaxcabine 15.5 Cu Ft Dual-Open Roof Box | Menabo Mania 320 Liter Roof Box |
|---|---|---|---|---|---|---|---|
| Capacity | not specified | not specified | 14 cu ft | 175L | 13 Cubic Feet | 15.5 cu ft | 320 liters/11 cubic feet |
| Shell Type | not specified | not specified | ABS | rotomolded hard case | Hard Shell, ABS | ABS and PMMA | not specified |
| Opening | not specified | not specified | dual-side | not specified | Double side | dual-side | not specified |
| Load Capacity | not specified | not specified | 165 lbs | not specified | 110 lbs | 130 lbs | 50 kg or 110 lbs |
| Water Resistance | not specified | Weather resistant, dustproof | waterproof | 100% Waterproof | Weatherproof | weather-resistant | not specified |
| Security | not specified | not specified | 2 keys and 2 straps | not specified | Security locking system with keys | built-in locking system | not specified |
| Installation | not specified | Cargo Roof Mount (sold separately) | not specified | not specified | No tool assembly | tool-free | quick fixing system |
| Vehicle Compatibility | not specified | not specified | all vehicles with roof rack | not specified | Fits vehicles with cross bars only | most crossbars | Compatible with all roof carriers |
| Dimensions | 36 x 18 x 18 in | 46 x 24 x 11.5 in | 62.2 x 31.5 x 13.4 in | 47.2"L x 18.4"W x 17.9"H | 56.3" L x 36.8" W x 16.25" H | 58.3 x 35.4 x 13 in | 55 x 14.3 x 31.5 in |
| Recommended Use | not specified | Gear, clothing, tools, dry food | not specified | not specified | not specified | family trips, camping | not specified |
| Vehicle Type | not specified | not specified | not specified | Truck | Car | not specified | not specified |
| Mount Type | not specified | not specified | Roof Mount | not specified | Roof Mount | not specified | not specified |
| Lockable | not specified | not specified | not specified | Lockable | Lockable | Lockable | not specified |
| Material | Steel | not specified | not specified | not specified | not specified | not specified | not specified |
| Weight | 87 pounds | 35.1 pounds | 44.8 pounds | not specified | not specified | 34.3 pounds | 19.8 pounds |
| Size | 36 x 18 x 18 inches | Cargo Case | 14 Cubic（Large） | not specified | 13 cu. ft.-16.25" H | 15.5 Cu Ft Black | 320 L |
| Color | Black | Black | Black | Black | Textured Black | Black | Black |
| Model | RKIH361818 | BX140-BLK | nncczujx4eU50hm4c2vYzgYDb1 | SR00011 | PT-ZTL-8188 | Black Cargo Box-61 | M000036100000 |
Frequently asked questions
Which alternative is best for heavy-duty truck storage?
The RKI 36x18x18 Steel Underbody Box is the top pick for heavy-duty underbody storage on trucks or SUVs. It is constructed from steel and measures 36 x 18 x 18 inches. The unit weighs 87 pounds, providing secure, compact storage underneath a vehicle. Its steel construction offers durability for rugged use.
What is the lightest roof box option available?
The Menabo Mania 320 Liter Roof Box is the lightest option at 19.8 pounds. It measures 55 x 14.3 x 31.5 inches and offers 11 cubic feet of capacity. This slim profile fits drivers who prioritize a compact size for standard roof racks. It is ideal for moderate cargo needs with quick, universal installation.
Which box offers the largest interior volume?
The Relaxcabine 15.5 Cu Ft Dual-Open Roof Box provides the largest volume at 15.5 cubic feet. It measures 58.3 x 35.4 x 13 inches and weighs 34.3 pounds. This model features dual-side opening for easy access and quick loading. It is a practical choice for families who value convenience over maximum aerodynamic performance.
Is there a lockable option for overlanding?
The Eylar SRX-175 Overlanding Cargo Case is lockable and designed for truck-bed or roof-rack overlanding use. It has a 175-liter capacity and measures 47.2 x 18.4 x 13.2 inches. This rugged, waterproof hard case is ideal for camping. Its size and weight may limit fit on smaller vehicles, so check your rack capacity.
Which roof box has a high load capacity?
The DNA Motoring 13 cu ft Hard Shell Roof Box supports a load capacity of 110 pounds. It measures 56.3 x 36.8 x 16.3 inches and features a weatherproof ABS shell. The dual-side opening allows for practical access. This model is suitable for buyers needing substantial weight capacity on vehicles equipped with cross bars.
What is the best budget-friendly dual-opening box?
The GarveeTech 14 cu ft Dual-Side Opening Roof Box is the best budget option. It offers 14 cubic feet of space and measures 62.2 x 31.5 x 13.4 inches. The dual-side opening provides flexible access for travelers. It prioritizes access and value over height, making it a solid choice for those seeking large storage on a budget.
Which case is best for protecting valuable gear?
The Pelican BX140R Cargo Case is best for protecting valuable gear with its premium, weather-resistant design. It measures 46 x 24 x 11.5 inches and weighs 35.1 pounds. This rugged case requires a separate roof mount. It has limited interior height, so it is ideal for flat or sturdy items that need secure transport.