Seeloc Washers work in combination with traditional bolts, screws, or studs to create an airtight seal around the fastener. The silicone contact surface features a continuous ridge that creates a 360° sealing barrier around the periphery of the washer face when compressed. The silicone rubber also forms a seal under the head of the associated fastener and makes full vertical contact with the threads/shank, making for a complete, high-pressure seal unlike any other.