The brake caliper operates just like a small hydraulic clamp designed to grip the brake rotor and bring your car to a halt. The brake caliper is a U-shaped device with a piston or pistons on one or both sides of the U. The brake pads ride on top of the brake caliper pistons, and the rotor spins in the channel of the U. When you hit the brakes, high-pressure fluid is channeled from the master cylinder down to the brake caliper where it pushes the piston or pistons inward. That brake caliper action moves the pads against the spinning brake rotor, and the friction stops your vehicle.
Each
Acura Legend brake caliper—there are four on your car, one at each corner—contains a piston or pistons in a bore, along with a pair of brake pads. When you hit the brake pedal, fluid is pushed up against the pistons in your Acura brake caliper, and the pistons push the brake pads, sandwiching the brake rotor between them.

The Acura brake caliper is generally made of steel or iron, to help it absorb some of that heat and prevent the brake fluid from boiling. Additionally, the Acura brake caliper has to be extremely strong to withstand the incredible forces generated as it tries to drag two tons of car to a halt. So make sure you take care of each Acura brake caliper on your vehicle. Be on the lookout for fluid leakage; if the seals in your Acura brake caliper go bad, they allow brake fluid to escape from the Acura brake caliper housing, resulting in poor pedal feel, pad contamination, and other dangerous conditions.