Most cars come with disc brakes in the front. Many models also have disc brakes in the rear. A caliper is part of the disc brake system. When stopping your vehicle, you press the brake pedal. The brake fluid flows from the master cylinder to the calipers. Brake fluid then applies pressure on the piston inside the caliper, pushing the brake pads against the rotors to slow/stop your car. A car can have either 2 or 4 calipers. If the car has rotors on all four tires, then it will have four calipers. If the car has two rotors and two drums, then it will come with two calipers in front and drums in the rear. The calipers can become contaminated, rusty, and start to leak brake fluid, and in some instances the caliper has phenolic pistons that can crack or break. Brake calipers absorb a lot of heat generated from the braking system. Over time, this heat can destroy or weaken the seals inside the calipers. Caliper servicing is usually done as part of a brake service job. Replacement of calipers is not always necessary, however you should have them checked routinely to prevent any problems that could arise.