What Is Shell Type? A Guide for Roof Cargo Boxes Buyers (2026)

Understanding Shell Type for Buyers

When you shop for roof cargo boxes, the first decision is often the shell type explained. This spec defines the primary material and structure of the container. It determines how your gear is protected from the elements and road debris. You will generally encounter two distinct categories: hard shell and soft shell. Each serves different needs and comes with specific trade-offs.

A hard shell box is constructed from rigid materials like ABS plastic, polyethylene, or fiberglass. These materials do not flex under pressure. The rigid structure provides superior protection against impact. It shields your items from falling branches, rocks kicked up by tires, and heavy snow loads. Hard shells are typically aerodynamic. They often feature sleek, low-profile designs that reduce wind noise and drag. This can improve fuel efficiency on long trips. The interior is usually fixed. You cannot change the shape to fit oddly sized items. However, the durability is high. These units resist UV degradation and extreme temperatures better than flexible alternatives.

A soft shell carrier uses heavy-duty fabrics like canvas or tarpaulin. These materials are stretched over a metal or plastic frame. The defining feature is flexibility. You can compress the box when it is empty. This makes storage much easier in your garage or shed. Soft shells are often lighter than hard counterparts. They can conform to the shape of your cargo. This allows you to strap down tall or irregular items that might not fit in a rigid box. However, they offer less impact protection. Rain and snow can seep through seams if the waterproofing fails. They are also more susceptible to tearing from sharp objects.

When comparing listings, look for these terms. Manufacturers will clearly label the construction method. Check the material list for details on thickness or weave. Consider your storage space and typical cargo. If you need maximum protection and have room to store the box, a hard shell is often the better choice. If flexibility and compact storage are your priorities, a soft shell may suit you better.

Hard Shell vs Soft Shell

Hard Shell

Hard shell boxes use rigid materials like ABS plastic or aluminum to form a solid, protective container. This structure offers superior defense against rain, snow, and road debris. The rigid shape also improves aerodynamics, which can help maintain fuel efficiency at highway speeds. Security is generally higher because these boxes often feature integrated locking mechanisms. For example, the Maxsa Innovations 17 cu ft Hard Shell Cargo Box provides a compact, aerodynamic solution with a 165 lb load capacity. However, hard shells are heavier and less flexible. They require roof racks or crossbars for installation and cannot be folded for storage when not in use. The Yakima SkyBox NX XXL 22 cu ft is another option that prioritizes secure, dual-sided access within a rigid frame.

Soft Shell

Soft shell cargo carriers, often called roof bags, are made from flexible, waterproof fabrics. They are designed to be packed onto roof racks or directly onto vehicles without rails. This flexibility allows for easy installation and removal, making them ideal for temporary storage needs. They are significantly lighter than hard shells and can be folded flat for compact storage in your garage. The Mockins 40 cu ft XXL Soft-Shell Roof Bag offers high capacity for bulky gear, weighing only 15.7 pounds. However, soft shells provide less protection against impacts and do not have the same aerodynamic profile as rigid boxes. They may flap in high winds if not secured tightly. The Sailnovo 21 cu ft Soft Roof Bag is a practical choice for cars lacking roof rails, prioritizing weight and ease of use over rigid protection.

Is Shell Type Worth Your Attention

Who needs it

You should prioritize this spec if you frequently transport sensitive equipment or valuable items. Hard shells provide rigid protection against impact, road debris, and harsh weather conditions. If you often carry bicycles, skis, or fragile gear, the superior defense of a hard shell is essential. It keeps your belongings dry and secure during long highway trips or off-road adventures. The aerodynamic shape of rigid boxes also helps maintain fuel efficiency at high speeds. For buyers who need maximum durability and weather resistance, this choice directly impacts the safety of their cargo. It is the right fit for those who view their roof box as a primary storage solution for expensive or delicate items that cannot withstand minor bumps or heavy rain.

Who can skip it

You can likely ignore this specific comparison if you only use your roof box for occasional, low-stakes storage. If you primarily haul camping tents, sleeping bags, or non-fragile items, the extra protection of a hard shell may be unnecessary. Soft shells offer a lighter, more flexible alternative that is easier to handle and store when not in use. Buyers with smaller vehicles or limited garage space might prefer the compact nature of a soft shell. In these cases, prioritize weight, ease of installation, and packability over rigid durability. If your gear is already waterproof and you do not drive in extreme conditions, the basic functionality of a soft shell will suffice for your needs without the added bulk or cost of a rigid structure.

Roof Box Glossary Terms

Shell Type

The primary material and structure of the box, such as hard plastic or soft fabric. This choice dictates overall durability, weight, and protection level against road debris and weather.

Capacity

The internal storage volume, measured in liters or cubic feet. A 300-liter box fits large suitcases, while smaller units suit weekend trips. Check dimensions to ensure your gear fits.

Opening

How the lid accesses the interior, typically single-sided or dual-sided. Dual-sided lids allow loading from both the driver and passenger sides, offering greater convenience in tight parking spots.

Load Capacity

The maximum weight the box structure itself can safely hold, often around 110 to 165 pounds. This is distinct from your vehicle roof’s limit. Exceeding this rating risks structural failure.

Vehicle Type

The specific car class the box is designed for, such as sedans, SUVs, or trucks. Ensure the box length and aerodynamic profile match your vehicle’s roofline for safe clearance and stability.

Water Resistance

The ability of the seals and lid to keep rain out. Look for gaskets and drainage channels. No box is fully waterproof, but high resistance keeps your gear dry in heavy rain.

Security

Features that prevent theft, such as integrated locks or locking mechanisms. Secure locks deter casual theft. Some models lock to the roof bars, ensuring the box stays attached during transport.

Recommended Use

The intended scenario, such as daily commuting, long-distance travel, or sports equipment. Match the box features to your habits. A bulky box suits skiing, while a sleek one suits city driving.

Quick picks

Our 6 picks

1

Maxsa Innovations 17 cu ft Hard Shell Cargo Box

Best for: compact storage and aerodynamic efficiency

Shell Type

Hard Shell (what this guide is about)

Capacity

17 cu ft

Opening

Dual-side

Load Capacity

165 lbs

Water Resistance

Waterproof

Vehicle Compatibility

Cars and SUVs with roof rack

View on Amazon: Maxsa Innovations 17 cu ft Hard Shell Cargo Box Affiliate link

This Maxsa Innovations roof cargo box offers 17 cubic feet of hard shell storage with a 165 lb load capacity. It measures 55.1 inches long, 35 inches wide, and 16.1 inches high, weighing 35.3 pounds. The aerodynamic design aims to reduce wind noise and improve fuel efficiency. It includes a locking system with two keys and fits most cars and SUVs with roof racks.

Pros

• 17 cubic feet capacity for luggage and gear
• 165 lbs maximum load capacity
• Aerodynamic shape reduces wind resistance
• Includes locking system with two keys

Cons

• 17 cu ft capacity is smaller than the 21-40 cu ft options on this list
• 165 lbs load limit is lower than typical hard shell boxes
• Only one height variation listed (16.1 inches)

Good fit if

• You need a compact hard shell for smaller vehicles
• You prioritize aerodynamic efficiency over maximum volume
• You require a locked storage solution for security

Skip if

• You need more than 17 cubic feet of space
• You plan to carry loads over 165 lbs
• You prefer the larger 21-40 cu ft options available

Verdict: Maxsa Innovations 17 Cu Ft Hard Shell Roof Box is a compact, aerodynamic choice for buyers who prioritize security and fuel efficiency over maximum storage volume. It suits those with smaller vehicles or lighter packing needs who want a secure, locked hard shell solution.

2

Sailnovo 21 cu ft Soft Roof Bag

Best for: Cars without roof rails needing flexible storage

Shell Type

Soft Shell (what this guide is about)

Capacity

21 cubic feet

Water Resistance

Waterproof

Installation

Tie-Down Strap

Dimensions

9.84 x 7.09 x 13.8 in

Vehicle Type

Car

View on Amazon: Sailnovo 21 cu ft Soft Roof Bag Affiliate link

This is a soft-shell roof bag with 21 cubic feet of capacity. It measures 7.09 inches wide and 13.8 inches high. The bag weighs 8.16 pounds and uses tie-down straps for installation. It is waterproof and fits cars without roof rails. You can choose between 21 or 15 cubic feet sizes. This option suits those needing flexible storage for smaller loads.

Pros

• 21 cubic feet capacity
• Waterproof construction
• Soft-shell design
• Lightweight at 8.16 pounds

Cons

• Smaller 21 cubic feet capacity compared to 40 cubic feet options
• Soft shell offers less rigid protection than hard shells
• No mention of integrated locking mechanism

Good fit if

• You need a waterproof bag for a car without roof rails
• You prefer a lightweight and flexible storage solution
• You want a soft-shell option for smaller cargo loads

Skip if

• You require hard-shell protection for fragile items
• You need more than 21 cubic feet of space
• You want a rigid box for high-speed travel stability

Verdict: Sailnovo 21 CuFt Soft-Shell Roof Bag is a practical choice for drivers with cars lacking roof rails who need waterproof, flexible storage for moderate loads. It fits those prioritizing weight and ease of use over rigid protection.

3

GarveeTech 12 cu ft Dual-Side Opening Roof Box

Best for: Dual-sided access and weather protection

Shell Type

Hard Shell (what this guide is about)

Capacity

12 cu ft (340 L)

Opening

Dual-side

Load Capacity

165 lbs

Water Resistance

Waterproof

Security

2 keys and 2 straps

View on Amazon: GarveeTech 12 cu ft Dual-Side Opening Roof Box Affiliate link

This is a hard shell ABS rooftop cargo box with a 12 cubic foot capacity and a 165 lb load limit. It measures 54.3 x 31.5 x 13.4 inches and weighs 39 pounds. The dual-sided opening system allows access from either side of the vehicle. It is waterproof and UV-resistant. It fits all vehicles with a roof rack. It includes two keys and two straps for security.

Pros

• Dual-sided opening for access from both sides
• 12 cubic feet (340 L) of storage space
• Hard shell ABS construction is waterproof and UV-resistant
• 165 lb maximum load capacity

Cons

• 12 cubic feet capacity is smaller than the 40 cu ft soft-shell options on this list
• 39 lb weight is substantial for handling
• Includes only two keys for the locking mechanism

Good fit if

• You need to access your cargo from the passenger side
• You have a roof rack and need extra storage for road trips
• You want a hard shell that protects against weather

Skip if

• You require more than 12 cubic feet of storage space
• You do not have a roof rack installed on your vehicle
• You prefer a lightweight soft-shell bag for easier handling

Verdict: GarveeTech 12 CuFt Hard Shell Roof Box offers dual-sided access and weather protection for drivers who need reliable storage. It suits those who prioritize hard shell durability over maximum capacity.

4

Mockins 40 cu ft XXL Soft-Shell Roof Bag

Best for: Vehicles without racks needing high capacity

Shell Type

Soft Shell (what this guide is about)

Capacity

40 cu ft

Water Resistance

Waterproof

Security

Combo lock

Installation

Buckle/ratchet straps, door hooks

Vehicle Compatibility

With or without roof rack

View on Amazon: Mockins 40 cu ft XXL Soft-Shell Roof Bag Affiliate link

This soft-shell roof bag offers 40 cubic feet of storage in a 72 by 48 by 20 inch footprint. It weighs 15.7 pounds and uses waterproof vinyl with reinforced seams. The design fits vehicles with or without racks, using hooks and straps for attachment. You get a complete kit with a roof mat and locks. It suits travelers needing flexible capacity without hard shell rigidity.

Pros

• 40 cubic feet of expandable storage space
• Waterproof vinyl construction with reinforced seams
• Fits vehicles with or without roof racks
• Includes roof mat and locking straps

Cons

• Soft material offers less impact protection than hard shells
• 72 inch length exceeds many vehicle widths
• Requires manual ratchet strap tensioning

Good fit if

• You need extra storage for large items like tents
• Your vehicle lacks crossbars or side rails
• You want a compact bag for off-season storage

Skip if

• You prioritize aerodynamic efficiency and fuel economy
• You need rigid protection for fragile gear
• Your vehicle roof width is less than 48 inches

Verdict: Mockins 40 CuFt Soft-Shell Roof Bag provides high capacity for bulky gear on vehicles without racks, but its soft shell and large footprint make it less ideal for speed or tight roofs.

5

Yakima SkyBox NX XXL 22 cu ft Hard Shell Box

Best for: Secure, dual-sided hard shell storage

Shell Type

Hard Shell (what this guide is about)

Capacity

22 cu ft

Opening

Dual-sided

Security

SKS lock

Recommended Use

Campers' gear, skis up to 215cm

Vehicle Type

Car

View on Amazon: Yakima SkyBox NX XXL 22 cu ft Hard Shell Box Affiliate link

The Yakima NX 22 is a hard shell roof cargo carrier with 22 cubic feet of storage. It features dual-sided access for loading from either side of your vehicle. Integrated SKS locks provide push-button security for your gear. The flattened floor and nano-texture finish offer a clean look and usable space. This unit suits families needing ample room for skis or camping equipment during outdoor trips.

Pros

• 22 cubic feet capacity for large gear loads
• Dual-sided opening allows access from both vehicle sides
• Integrated SKS push-button locking system
• Flattened floor design maximizes usable interior space

Cons

• 22 cubic feet is smaller than the 40 cubic feet soft-shell options on this list
• Single color option limits aesthetic customization
• Height varies between 16 and 16.5 inches across models, requiring specific fitment checks

Good fit if

• You need dual-sided access for tight parking spots
• You prioritize high security with integrated SKS locks
• You have a vehicle roof rack compatible with Yakima mounts

Skip if

• You require maximum volume over 22 cubic feet
• You prefer a soft-shell roof bag for lower cost
• You need multiple color choices for your vehicle

Verdict: The Yakima NX 22 Hard Shell Roof Box fits drivers who value secure, dual-sided access and a sleek hard shell design over maximum raw volume.

6

Mockins 40 cu ft XXL Roof Bag

Best for: cars without roof racks needing high volume

Shell Type

Soft Shell (what this guide is about)

Capacity

40 cu ft

Water Resistance

Waterproof

Security

Combo lock

Installation

Buckle and ratchet straps

Vehicle Compatibility

With or without roof rack

View on Amazon: Mockins 40 cu ft XXL Roof Bag Affiliate link

This soft-shell cargo bag offers 40 cubic feet of storage with dimensions of 72 by 48 by 20 inches. It is constructed from 840D vinyl and features waterproof zippers under a protective flap. The design works with or without crossbars, using door and trunk hooks for attachment. It includes a roof mat and multiple straps to secure your gear during travel.

Pros

• 40 cubic feet of XXL storage capacity
• 840D vinyl shell with waterproof zippers
• Installs on vehicles without crossbars
• Includes roof mat and carry bag

Cons

• Heavier at 16.5 pounds than hard shells
• Soft material offers less aerodynamic efficiency
• No rigid structure for heavy load stability

Good fit if

• You need extra space for bulky gear
• You drive a car without roof racks
• You want a waterproof soft-shell option

Skip if

• You require a rigid hard-shell design
• You prioritize aerodynamic fuel efficiency
• You need a lightweight carrier under 10 pounds

Verdict: Mockins 40 CuFt Soft-Shell Roof Bag is a flexible solution for cars lacking roof racks. It suits buyers who need maximum volume and waterproof protection for soft items like tents or sleeping bags.

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Frequently asked questions