M3 M4 M5 M6 M8 Black Carbon Steel Hex Flange Nylon Insert Lock Nut Self-locking Nylock Locknut Material : Carbon Steel (black zinc-plated) Size:M3 M4 M5 M6 M8 Note:Some oil is applied to the surface of the nut, it is not stains or rust, those are anti-rust oils, these oils are used to prevent rust
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