Serrated Flanged Conical Hexagonal Nut Black Oxide 5/8-11 Grade 8

An irregularly shaped thread at the top of the nut grips the bolt for a stronger hold than nylon-insert locknuts. They thread on from the bottom of the nut, allowing more threads to engage the bolt before tightening for easier installation than center-lock distorted thread locknuts. The strength of the bolt should match the strength of the nut to prevent damaging threads. They're not reusable. Comparable in strength to Grade 8 bolts, they're about 25% stronger than medium-strength steel locknuts.

Zinc-plated steel locknuts resist corrosion in wet environments.