weideer 50PCS M4.2 Universal Fender Liner Screw U Nut Kit,Engine Splash Shield Hex Head Screw U Clips,Automotive Body Screws Clips

A small hardware kit that solves a big headache

I keep a few “consumables” in the shop that quietly save projects: trim clips, hose clamps, and fasteners for underbody plastics. The weideer fender liner screw and U-clip kit has joined that list. It’s a straightforward set—25 hex-head screws with 16 mm washer faces and 25 matching U-nuts—meant for securing fender liners, engine splash shields, bumpers, door panels, and trim. On paper that’s nothing exotic, but after using this kit across a couple of repairs and a fender flare install, I came away impressed by how consistently it just works.

What you actually get

• 25 screws: M4.2 x 20 mm (#8 x 3/4")
• 7 mm hex head, with a broad 16 mm washer face
• 25 U-nut clips to match
• Intended panel thickness: 0.025" to 0.150"
• Required center-of-hole-to-edge distance: 3/8"

The M4.2 designation is typical for a self-tapping automotive body screw. Paired with the included U-nuts, you don’t need a pre-threaded hole; you only need proper alignment and a reasonable pilot/slot. The 7 mm hex is convenient for a 1/4" drive socket or nut driver, and the 16 mm washer face provides enough coverage to grip common plastic liners without chewing through them.

Fit and compatibility: what matters before you buy

Two specs determine whether a kit like this will behave like OEM or turn into a compromise: panel thickness and the offset from hole center to the panel edge.

• Panel thickness (0.025"–0.150"): This comfortably covers most automotive plastics and thin sheet metal edges where U-clips are normally used. If you’re trying to clamp a double layer of thicker steel or heavy aftermarket flare brackets, check your combined thickness—beyond ~0.150", the clip won’t bite as designed.

• Center-of-hole-to-edge (3/8"): This is the distance the U-clip expects from the panel edge to the fastener hole. If your panel holes sit too close to the edge, the clip won’t center correctly; too far and you’ll be fighting alignment. On factory liners and bumper edges I tested, this spec lined up well.

The screws are #8/M4.2 size, which is common across many North American and Asian vehicles for liners and splash shields. If your vehicle uses larger M5/M6 flange bolts for undertrays, this kit isn’t a drop-in replacement. But for most fender liners, inner splash shields, and trim flanges, the size is right in the sweet spot.

Materials and finish

The hardware is metal with a black coating. It’s clearly not raw bright zinc, and it isn’t stainless. In the real world that’s fine for underbody plastics as long as you don’t subject the hardware to constant salt spray without rinsing. After several weeks of mixed weather and a couple of car washes, I didn’t see flaking or red rust starting on exposed heads. The black finish also disappears visually against typical black liners and bumper plastics, which is nice when you want a “factory” look rather than shiny fasteners dotting the wheel wells.

The U-clips have a good spring to them. They slide on with firm tension and don’t deform easily when you tighten the screw. That’s important: soft clips are what lead to loose shields and that familiar highway buzz.

Installation: straightforward, with a few best practices

My use cases included reattaching a loose engine splash shield and replacing a handful of missing fender liner fasteners on an older SUV, then installing aftermarket fender flare sections on a truck where the original clips had long since given up. In each case:

• I clipped the U-nuts onto the panel or substructure edge first, aligning the threaded hole over the panel hole.
• I used a 7 mm nut driver to spin the screws in by hand until seated.
• I switched to a 1/4" ratchet for final snugging.

Tips that helped:

• Pre-align everything. You want the U-clip’s hole centered under the panel hole. If you’re off, the screw will try to cut its own path, and you can cross-thread the clip.
• Use low torque. These are small fasteners. 2–3 N·m is plenty for plastic liners. Over-torque can distort the plastic or strip the clip.
• If the panel hole is oversized, add a small rubber or nylon washer under the 16 mm washer face to spread load and reduce vibration.
• A dab of silicone or light anti-corrosion spray on the screw threads can help if you live in the rust belt, but don’t overdo it—too slippery and you may over-tighten without feeling resistance.

Thread engagement felt clean. The screws cut into the U-nuts predictably and didn’t exhibit the gritty “tearing” feel you get with poorly formed threads. The washer face sat flat on my liners and didn’t bite into the plastic.

Performance under the car

The real test is less about installation and more about what happens after a few drives. With the splash shield re-secured, the front-end rattle I’d been chasing disappeared. I intentionally drove over some poorly maintained concrete and through a washboard gravel section; nothing backed out or loosened. On the fender flare install, the clips held alignment well and didn’t shift when the panel flexed slightly during a hand wash.

I also like the 7 mm hex head choice. It’s small enough to fit into tight wheel-well recesses, but not so small that a slightly worn socket will round it off. And if you prefer a screwdriver, the head accepts a standard driver bit (though a nut driver gives you better control).

Limitations and small gotchas

• Not stainless: For coastal climates or vehicles that see heavy salt, stainless hardware is ideal. This kit’s coating did fine in my use, but if you’re looking for multi-year, no-maintenance confidence under severe corrosion, plan for periodic inspection—or choose stainless knowing you might trade away the black, OEM-like look.

• Size constraints: If your vehicle uses M5/M6 underbody bolts or push rivets in key positions, this kit won’t replace those. It’s best as a like-for-like for #8/M4.2 screw-and-clip applications, or as a smart upgrade where push pins kept failing.

• Washer diameter: The 16 mm washer face is a good universal size, but on oversized slotted holes, it can be marginal. That’s where adding a larger nylon washer is handy.

• Panel range: If you’re clamping very thin film-like liners, consider backing the area with a small reinforcement tab to avoid “potato-chipping” the plastic.

None of these are deal breakers, but they’re worth noting so you set expectations and prep the right accessories.

Who benefits most from this kit

• DIYers who regularly service their own cars and want a reliable stash of body fasteners.
• Shops needing a go-to size for common fender liner and splash shield work.
• Anyone installing aftermarket fender flares or mud guards where new mounting points mirror OEM #8 screw locations.
• Owners of older vehicles where clips have rusted or disappeared and push rivets just won’t stay put anymore.

If you’re outfitting a single project, 50 pieces is a generous amount. If you work on multiple vehicles, it’s the right volume to keep in a drawer and not think about reordering after every job.

Practical tips for selecting and using it

• Measure your panel thickness and confirm it sits within 0.025"–0.150".
• Check the edge distance to ensure the 3/8" spec aligns with your panel’s hole layout.
• Test-fit one clip and screw before committing to the entire panel to confirm engagement and alignment.
• Keep a 7 mm nut driver in your glovebox; these are the kinds of fasteners you sometimes replace in a parking lot after discovering a dangling shield.

Verdict and recommendation

After using the weideer kit across multiple repairs, I’m confident recommending it. The size, thread form, and U-clip tension hit the mark for typical fender liner and splash shield applications. Installation is simple, the black finish looks OEM, and the hardware stayed tight and rattle-free in real use. It’s not stainless, so it’s wise to inspect periodically in harsh climates, and it won’t substitute for larger M5/M6 hardware where required. But as a dependable, budget-friendly stock of #8/M4.2 screw-and-clip fasteners, it earns a spot in the shop.

I recommend this kit for anyone who needs a reliable, no-fuss solution to reattach liners, undertrays, and trim. It’s the kind of small purchase that prevents bigger headaches—and keeps your car quiet, tidy, and properly buttoned up.