Hayes dominion a4 j unit disc brakethis brilliant disc brake is specifically engineered for mtb use as it gives you powerful and reliable stopping performance. It features a four piston caliper that's designed especially for the rigors of dh and enduro racing as it meets the demands of the most aggressive trail conditions and riders. Providing a firm engagement between the pads and rotors, its caliper keeps you in full control thanks to its fast and precise braking power.low effort mtb disc brakewhether you're competing or riding after work with your buddies, this version's solid lever features a specific pull curve to balance on demand pressure modulation with ease. As a result, you'll be able to enjoy its simple and easy to pull design for an effortless braking feel and control as you weave between the trails.perfect for riders with smaller hands, this sfl small freaking lever version makes it incredibly easy to actuate as you carve your way across the mountain. To top it off, its k2 hose is constructed from a woven kevlar construction to provide the stiffest hose possible for maximum power transmission.features use mtb type sfl small freaking lever version piston 4 piston caliper 74mm post mount brake fluid dot 5.1 hose k2 hose from woven kevlar weight 303g approxbuy hayes components from chain reaction cycles, the world's largest online bike store.