Galespeed Thumb-Brake Rear Brake Master Cylinder - The GALE SPEED rear master cylinder has a 12mm piston diameter and was designed to match the general racing lever ratio . Forged 6061 and 3D machined body with a T6 heat treatment for strength and corrosion resistance. Adjustable mounting points slide to widen mounting points for universal applications. NOTE: Fluid tank not required when brake hoses are connected directly