Left. Right. 1 Piston Caliper. A Bushing, typically made of rubber, used to provide a surface for the disc brake Caliper Guide Pin to move freely. A rubber boot used to protect the disc brake Caliper Guide Pin from dirt, debris and moisture to prevent corrosion. Disc Brake Caliper Bushing. Disc Brake Caliper Pin Seal. From 03/05. From 03/17/2005. Included with: Caliper, Seal kit.