The 12mm size is well-suited for the Moto-Master Supermoto Racing Caliper. Using a stock brake setup on a 320mm rotor? Add this to your system to give a little more power to your brakes without being too stiff of lever feel. The brake lever position is adjustable allowing it to suit any preference, and an optimal leverage ratio built into the design gives you maximum power with just one finger. The direct pressure point provides great feedback which ensures optimal control. Black anodized and laser etched aluminum filler cap to complete the package. Brake light switch available separately. Standard 7/8" clamping diameter, fits off-road handlebars (Both small bars and fat bars have 7/8" diameters on the ends where grips and levers bolt on.) Radial Master Cylinder Instructions Radial master cylinder mounting instructions Brake fluid reservoir mounting instructions Brake fluid reservoir filling instructions for racing use