5/16英吋 內齒鎖緊墊圈 | 鋼 三價鋅 (5000個/包)

The trivalent zinc finish handles my shop’s humidity without a speck of rust, which is a huge relief for a 5000-pack. These #5s bite into the bolt head firmly and hold torque well under my drill’s vibration, exactly what I needed.

Finally found a bulk box that actually holds up under my workshop's constant vibration testing—the zinc coating on these is smooth and even, no flaking. They bite into the steel like they're supposed to, even after multiple tightening cycles.

Bought a full box for a batch of small assemblies, and the trivalent zinc finish on these is more consistent than what I've seen from other suppliers. They bite down evenly without distorting.