Product details:

EPDM rubber (Neoprene) is an extremely durable synthetic rubber membrane - Inside Diameter .25 inch | Outside Diameter 5/8 inch | Thickness .145 inch - Passivated finish with an A70 durometer hardness304 stainless steel for long life corrosion resistance - Rubber bonded to stainless steel creates a corrosion resistant washer that cushions bolt and screw heads and seals joints to prevent leaks. The rubber washer provides superior cushioning, sealing and vibration dampening. Age Group: adult.