Before the introduction of the euro, francs were also used in France, Belgium and Luxembourg, while Andorra and Monaco accepted the French franc as legal tender (Monegasque franc).
Inside the caliper is a brake pad, a small block of friction material backed with a metal plate. When you step on your brake pedal, pistons inside the caliper cause it to apply pressure to the brake pad which squeezes the rotor, causing the car to slow or stop.
Calipers consist of a housing, piston(s), seals, dust boot, and a bleeder valve. The pistons can be made of phenolic or steel. The phenolic piston consists of a phenol-formaldahyde resin that is light weight, heat resistant, non-corroding, and resists heat transfer.