Shimano BR-MT520 4-Piston Hydraulic Disc Brake Caliper Front or RearThe Shimano BR-MT520 Hydraulic Disc Brake Caliper uses a strong 4 piston design to give excellent control and finesse of your braking power. There is a Wider contact area of dual diameter opposed-piston design. The rapid initial pad contact accentuates your brake power. Compatible as a front or rear caliper.689228879430