Product Details: CNC Machined from Billet 6082-T6 Aluminium Manufactured in Devon, UK 13mm Bore for increased braking pressure Slotted mounting hole Fully road legal Hard wearing black anodised finish Compatible with thumb brakes In-depth Information Solid Billet CNC Machined HEL brake master cylinders are precision machined from race grade solid billet 6082-T6 aluminium - maximising weight and minimising material used. Machined and forged components are NOT comparable, so be sure to insist on machined for the very best design, precision construction and finish on the market. Increased Braking Pressure The majority of motorcycles use an 11mm bore rear master cylinder as standard. HEL rear master cylinders utilise a 13mm bore to increase the amount of pressure.