4 The calipers used on the MP Brakes kit are a floating, pin-mounted style. A floating caliper (also called a sliding caliper) is able to move/float with the rotor. When applying the brakes, a piston on one side of the rotor pushes the inner brake pad until it makes contact with the braking surface, and then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the rotor. If they were a fixed caliper, the caliper would not move/float, which makes them less tolerant of rotor imperfections. It also uses opposing pistons to clamp from each side of the rotor, and is more complex and expensive than a floating caliper.