Specification:
manufacturer? roof load limit.

2. Dimensions

Length, width, and height of the carrier.

Must fit the vehicle? roof and allow easy door and hatch access.

Roof boxes: typically 130?90 cm long, 70?0 cm wide, 30?5 cm high.

3. Material

Steel: Strong, durable, may rust if not coated.

Aluminum: Lightweight, corrosion-resistant, often more expensive.

Plastic / Polypropylene: Lightweight and aerodynamic for roof boxes.

4. Mounting Type

Roof rails: Attaches directly to raised or flush rails.

Crossbars: Fixed bars that run across the roof.

Suction mounts / Magnetic mounts: Rare, usually for temporary carriers.

5. Compatibility

Must match the car? roof type:

Bare roof

Raised rails

Flush rails

Fixed mounting points

Check universal vs. vehicle-specific fit.

6. Aerodynamics

Carriers designed to reduce wind drag and noise.

Features like curved or tapered shapes are common in roof boxes.

7. Security

Lockable clamps or lids to prevent theft.

Some have integrated locks for crossbars or cargo boxes.

8. Expandability & Accessories

Some carriers allow:

Ski or snowboard mounts

Bike racks

Kayak / canoe mounts

Additional tie-down points

9. Opening Mechanism (for cargo boxes)

Side-opening, dual-side opening, or rear-only access.

Dual-side openings offer more convenience.

10. Weather Resistance

Waterproof or water-resistant designs.

UV-resistant coatings to prevent fading.

11. Weight of Carrier Itself

Steel racks: heavier (~15?0 kg)

Aluminum racks: lighter (~8?2 kg)

Plastic boxes: ~20?5 kg depending on size.

12. Certifications / Standards

ISO 11154, TUV, or SAE standards for load safety and quality assurance.