The Capri Tools Disc Brake Piston Tool is a must have tool for changing your rear disc brake pads or rotors. Used with a 3/8 in. ratchet, the tool rotates and compresses rear disc brake piston back into the brake caliper, so you can reinstall the brake caliper after changing brake pads or rotors. Unique cube design provides 5 drive pin configurations to fit rear disc piston of most vehicles. For front disc brakes, use the Capri Tools Disc Brake Pad Spreader to easily reset the piston (sold separately).