Forge Fix-Shake-Proof-Washer-ZP-Forge Fix-SHPWASH12B-These-Forgefix-Shake-Proof-washers-are-designed-to-allow-a-secure-fastening-preventing-loosening-of-the-fastener-by-either-movement-or-vibration-Also-known-as-serrated-washers-or-star-washers-they-have-serrations-that-extend-radially-inward-&-or-outward-to-bite-into-the-bearing-surface-This-type-of-washer-is-effective-as-a-lock-washer-when-used-with-a-soft-substrate-such-as-aluminium-or-plastic-The-washers-are-bright-zinc-plated-for-i