Nut, M5 Nylon Insert Lock

Used a few of these on my 3D printer's vibration-prone Z-axis and they haven't budged in weeks. The nylon insert grabs nicely without damaging the bolt threads.

These lock nuts held tight on my motorcycle's license plate bracket even after a bumpy ride down a gravel road. The nylon insert made them noticeably easier to start threading by hand compared to standard lock washers.

The nylon insert grips the threads right away, so I didn't need to crank it down with extra force to keep it from backing off. I've been using these on a small bracket that gets a lot of vibration and they've held firm for weeks now.