Left. Right. A cover, typically made of plastic or rubber, which protect the disc brake Caliper guide pin heads from dirt, debris and moisture, to prevent corrosion. A protective cap placed on a brake bleeder screw. Disc Brake Caliper Bushing. mount kit. Brake Bleeder Screw Cap. COVER - Dust. Disc Brake Guide Pin Cover. Disc Brake Slide Pin Cover. Included with: Caliper.