The ST1 O-Ring 2 Pk End Cap is a pack of two rubber rings that are used to seal the end cap of the Carlisle ST1 spray gun. The end cap is a part that covers the back of the spray gun and protects the internal components. The O-rings prevent any leakage or damage to the spray gun and ensure a reliable and safe operation. The O-rings are made of durable and flexible material that can handle high pressure and temperature. The ST1 O-Ring 2 Pk End Cap is one of the parts included in the Carlisle ST1 O-Ring Kit Wetted Parts 336420, which contains all the necessary O-rings and wetted parts for the ST1 spray gun.