Metallics JMNYN305BLK Nut M3-0.5 Nylon Insert Locknut Bl (Jar 100)

It's an M3-0.5 metric thread, so it mates with M3 screws and bolts at 0.5 mm pitch, the standard coarse pitch for M3. The nylon insert grips the male thread to resist loosening under vibration.

No. M3-0.5 is metric and #4-40 is inch series; the pitch and diameter don't match and forcing them strips both. Match these to M3 screws only. If your screws are #4-40 or #6-32, you need the inch-series nylon insert locknut in that size instead.

100 nuts, supplied in a jar rather than a loose bag, which keeps small M3 hardware contained on a cart or bench.

A nylon insert locknut like the M3-0.5 JMNYN305BLK works by the nylon collar deforming around the male thread, so each removal cuts into the grip. Reuse is possible a few times but the prevailing torque drops each cycle. On anything that holds a cover, bracket, or device in place, fit a fresh nut from the jar of 100.

On M3 hardware the nylon insert nut is usually the easier call: it resists vibration loosening without needing a separate washer in the stack, and there's one less tiny part to drop inside an enclosure. A plain nut with a split washer is the choice where heat is a factor, since the nylon in these nuts is a plastic element and loses grip at elevated temperature.

Yes, the JMNYN305BLK is the black version. For electrical enclosure and panel assembly where the fastener is visible, the black finish blends with black-painted panels and trim rather than standing out like bright plated hardware.