Left. Right. 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 Bushing. Upper. Caliper dust cap. Disc Brake Caliper Slide Boot. Disc Brake Caliper Slide Bushing. Guide cap. Included with: Caliper assembly, Seal kit and caliper.