Brake Calipers
Calipers sold separately, for building your own kit or replacing an existing caliper.
Piston count and distribution
More pistons distribute pressure across the pad more evenly, resulting in more even wear and better performance under repeated braking. However, an oversized front caliper on a rear axle unbalances the braking: maintain the original distribution, or correct it with a proportioning valve.
Bracket and disc
A caliper is never mounted on its own: it needs a bracket with the bolt spacing of your steering knuckle and a disc with the correct diameter and thickness.