This is a dual piston actuated mechanical disc brake caliper which provides precise clamping force. This translates into even pad and rotor wear because the rotor does not need to flex to one side during braking. We added a simple cable barrel adjuster to make fine tuning easy. All of this in an incredibly thin 40mm, 146g package, that works with any drop bar levers on the market. Rotors and adapters are sold separately.