[Easy Installation]-Product thickness is relatively thin, please be careful when installing. Please do not use too much force. [Function] - Lock washers add a spring force between the fastener head and the substrate to increase friction and resistance. [Application]-Widely used in product maintenance of vehicles, toys, wheels, etc. Material Selection Guide: -65Mn Black Oxide Locking Washer 65Mn Spring Steel is the perfect material for spring washers due to its superior strength. Black oxide finish provides better corrosion resistance in dry environments. -Stainless steel locking washer corrosion resistance, rust resistance, strong and durable.