M3.5 (3.9mm x 9mm) Nord-Lock Washer in Zinc Flake, per pair

Nord-Lock washers, also known as wedge-locking washers, secure bolts with tension instead of friction. Working as a pair, these washers create a wedge-effect underneath the bolt head or nut so that the joint is prevented from loosening unintentionally. Nord-Lock washers are quick and easy to install and remove, and they are reusable. Supplied as a glued pair, they are appropriate for use in vehicles, for DIY and for watersport equipment. Most sizes are available in two external diameters: the smaller standard type, and the larger SP type listed here.