Qjaiune 50pcs Rubber End Caps, 1/8 Inch / 3mm Screw Thread Protector Caps - White Vinyl, Flexible Bolt Covers

A small, useful fix for sharp ends and scuffed surfaces

Sometimes the simplest add-ons make the biggest difference. These small rubber end caps have become a staple in my shop for taming sharp screw tips, finishing rod ends, and adding a touch of protection where bare metal meets skin, cables, or flooring. They’re white, soft, and flexible, sized for a 3 mm inner diameter with about 15 mm of usable depth. You get fifty in the bag—enough to outfit a project and still have spares in the drawer.

I took them through a handful of tasks—covering exposed screw tips on light-gauge sheet metal, capping small steel rods, and dressing up the ends of fasteners inside cabinets—to see how they fit, hold, and wear.

Build and material

The caps are made from flexible vinyl rubber that feels soft without being gummy. They’re not brittle, and they don’t carry a strong odor out of the bag. The wall thickness is substantial enough to resist tearing when stretched over threads, yet supple enough to conform tightly once seated. The white finish is clean and uniform across the batch I used, with consistent molding and no flashing at the rim.

I’d classify the material as “shop friendly”: it grabs threads well and rebounds after being pressed or flexed. It’s also a decent electrical insulator for low-voltage, low-stress applications, though I wouldn’t treat it as a safety-rated solution for anything involving mains voltage or high temperatures.

Fit and sizing accuracy

The published sizing—3 mm inner diameter, tight up to about 3.5 mm—is accurate in practice:

• M3 screws (3.0 mm OD): Slip on easily and seat firmly.
• M3.5 screws (≈3.5 mm OD): Very snug. They go on with a bit of effort and stay put.
• #6 wood/metal screws (≈3.5 mm OD): Tight but workable; a dab of soapy water helps with installation.
• 1/8-inch nails or rods (3.2 mm OD): Just about perfect.
• 2–2.5 mm rods: The fit is loose. They’ll go on but won’t necessarily stay without adhesive.
• 4 mm rods: Too large for these caps.

Depth-wise, the inner cavity of about 15 mm is generous for covering sharp points, screw threads, and short rod ends. If your application requires less depth—say you only need 5–7 mm of coverage—you can trim the caps cleanly with a sharp utility knife or flush cutters.

If you plan to use these on furniture “legs,” note the size: they’re ideal for thin, round metal legs or wire frames (think 3–3.5 mm rod), not standard chair or table legs. For typical furniture, you’ll need a much larger cap.

Installation tips that actually help

These are friction-fit covers, so installation comes down to technique:

• For a tight fit on #6 or M3.5 threads, a quick dip in warm water softens the material and makes stretching easier.
• A drop of dish soap or isopropyl alcohol acts as a temporary lubricant; alcohol evaporates quickly and leaves no residue.
• To keep a cap on undersized rods (≈2–2.5 mm), a tiny dab of clear silicone sealant inside the cap provides grip without making removal difficult.
• Trimming: Use a fresh blade and a simple miter box or scrap wood as a cutting guide to keep cuts square.

In my tests, once seated, the caps stayed put—even on screws subjected to vibration on a small fan housing. No creep or backing off over a week of runtime.

Real-world uses I tried

• Exposed screw tips on light-gauge metal: I used these to cover the sharp ends of sheet-metal screws on a backyard run. Sliding the caps over the protruding threads turned a scratch hazard into a smooth, rounded surface. The caps handled the minor thread burrs without tearing.

• Protecting cabinet contents: A few cap ends on fasteners inside a utility cabinet stopped tool bags and cables from snagging, and the white caps make it easy to see where the sharp bits used to be.

• Finishing small rod ends: On 3 mm steel rod used for a lightweight frame, the caps added a clean, finished look while preventing the ends from scratching nearby surfaces.

• Cable and wire protection: The inner diameter fits 12 AWG jacketed wire and some 3 mm cable bundles. I used them as temporary protective boots over cut cable ends; the snug fit kept them from falling off in the bin.

Durability and weathering

Indoors, these hold up very well. The material resists cracking and doesn’t harden noticeably over a few weeks of use. On coarse zinc-plated threads, I didn’t see immediate wear-through, though any soft cap will eventually abrade if it’s repeatedly removed and reinstalled on sharp threads.

Outdoors, vinyl in white is more vulnerable to UV than black rubber or EPDM. After several weeks of full sun, I noticed slight dulling and a hint of yellowing on the most exposed caps. They remained flexible and intact. If you need multi-season, high-UV performance, I’d consider switching to black caps or a rubber formulated for UV resistance. For seasonal use or shaded installs, these are fine.

Temperature-wise, a quick freezer test kept them flexible enough to install (with more effort), and they didn’t go mushy in afternoon sun. They’re not designed for hot exhausts or high-heat equipment, so keep them away from anything that routinely exceeds warm-to-the-touch.

Aesthetics and cleanup

White looks tidy and makes protrusions obvious, which is great for safety. The trade-off is that white shows dirt. The finish cleans up with a damp cloth and mild soap. On textured or painted surfaces, the caps don’t transfer color, and they don’t leave marks on floors—one of their nicer qualities when used under small metal feet.

What these are not

• Not a one-size-fits-all furniture foot: These fit rods and screws around 3–3.5 mm, not standard chair legs.
• Not a permanent weather-cap solution: For long-term rooftop or marine environments, look for UV-stable black rubber or heat-shrink end caps.
• Not a substitute for certified insulation: Fine for basic abrasion protection; not a safety device for electrical work.

Value

Fifty pieces go a long way. When I outfitted a small project, I used a dozen and still had plenty left for the shop. The consistent molding, reliable fit across the batch, and versatile size make the pack good value if your work regularly involves small screws, rods, or cable ends. White is a nice neutral for indoor applications and a visible cue for safety checks.

Pros and cons

Pros:
- Accurate sizing for 3.0–3.5 mm applications, including M3/M3.5 and #6 screws
- Soft, flexible material that grips threads and protects surfaces
- Easy to trim for shallower coverage
- Clean white finish and consistent quality across the pack
- Useful for both mechanical protection and light insulation

Cons:
- Loose on sub-2.5 mm rods without adhesive
- White can show dirt and may yellow with prolonged UV exposure
- Not suitable for typical furniture legs or larger-diameter rods

Final thoughts and recommendation

These rubber end caps are straightforward, well-made, and genuinely useful across a range of small-diameter tasks. They turn sharp screw tips into rounded, safe ends; they keep rods from scratching nearby surfaces; and they add a neat finish to projects that otherwise look a bit raw. The sizing is honest, the grip is reliable, and installation is simple with a couple of easy tricks.

I recommend them if your work or household fixes routinely involve screws, nails, or rods in the 3–3.5 mm range—think small metal frames, #6 screws, M3/M3.5 hardware, or insulated wire ends around 12 AWG. Measure what you’re capping first; if you’re under about 2.5 mm, you’ll want a smaller size, and if you need outdoor, long-term UV resilience, consider a black rubber alternative. Within their intended size and use, these caps solve a lot of small annoyances for very little cost, and they earn a permanent spot in my kit.