X AUTOHAUX U-bolt Roof Box Clamps 4-Pack — 83mm Internal Width, Fits up to 40mm Crossbars with Lock Nuts

These X AUTOHAUX U-bolt clamps are a complete 4-piece mounting kit designed to secure most rooftop cargo boxes and carriers to crossbars up to about 40mm thick.

If you need a straightforward replacement or upgrade for the hardware that fastens your rooftop cargo box, this kit supplies iron U-bolts, rubber washers, plastic backing plates, lock nuts, and straps so you can restore or improve the connection between box and rack. The components are sized for an 83mm internal clamp width and include eight heavy lock nuts for a reliable hold; materials combine metal and engineered plastics for corrosion and wear resistance. These parts are intended for many universal carriers but are not compatible with Thule-brand racks.

Will these clamps fit my roof box and crossbar?

Measure the gap and mounting points on your box and crossbar to confirm compatibility before buying. The clamp's internal width and thread spacing determine fit, and this kit is made for common aftermarket carriers rather than brand-specific systems.

• Internal clamp width: 83mm (3.27 in)
• Center-to-center thread spacing: 90mm (3.54 in)
• Screw diameter: 7.5mm (0.3 in)
• Suitable for rail/profile thickness: up to ~40mm (1.57 in)
• Not compatible with Thule car rack systems

How do these parts protect my vehicle and cargo during travel?

The kit includes rubber gaskets and plastic support plates that cushion contact points and increase friction so the box stays put while driving. Properly tightened lock nuts and secure straps reduce movement and minimize the risk of abrasion or scratches to roof paint and box finish.

• Rubber washers absorb vibration and protect paint
• Plastic backing plates distribute clamping force evenly
• Heavy lock nuts resist loosening under road stress
• Included straps help hold the box during installation and transit

What materials are used and how durable are they?

Components blend iron fasteners with plastic support parts and rubber seals to balance strength and corrosion resistance. The iron bolts provide load-bearing capacity while the plastic and rubber resist wear, temperature changes, and surface damage during repeated use.

• Iron bolts for structural strength and rigidity
• Plastic boards for impact distribution and anti-scratch protection
• Rubber gaskets for vibration damping and grip
• Lock nuts designed for secure fastening under load

How easy is installation and what comes in the package?

Installation is straightforward with basic tools; parts are sized for common aftermarket boxes and mounting holes. The kit contains everything needed to replace worn or missing fasteners so you can reattach your rooftop carrier without searching for multiple components.

• Included: 4 iron U-bolts, 4 rubber washers, 4 plastic backing plates
• Plus: 8 heavy lock nuts, 2 straps, 1 black sticker for alignment
• Small, lightweight components for easy storage when not installed
• Check your box measurements and any fitting guides or videos before starting

Who is this for: This X AUTOHAUX clamp kit is aimed at vehicle owners who use universal rooftop cargo boxes and need reliable replacement hardware—especially those with non-Thule crossbars up to 40mm thick. It's suitable for DIYers restoring a carrier, renters who bought a used box missing fasteners, and anyone wanting a compact, durable set of mounting parts to secure gear for road trips and everyday hauling. Always confirm measurements and compatibility with your box and crossbar before purchase.