These type 18-8 stainless steel neoprene bonded washers, also know as sealing washers are strong and provide a tight grip around the screw. The neoprene rubber is bonded to the washer and offers a good watertight seal. Type 18-8 stainless steel has a high resistance to rust and corrosion and may be mildly magnetic. Each Marine Bolt Supply pack is individually labeled and conveniently heat sealed in reliable poly bags for safe shipping.