HEL Solid Billet Twin Port Rear Master CylinderHEL Solid Billet Twin Port Rear Master Cylinder Description The new HEL Performance TWIN rear master cylinder is once again fully CNC machined from solid aluminium billet to give an additional product to our ever expanding range. The rear master cylinder has been designed in a square format to sit and blend effortlessly behind the heel plate on all models. It features a 13mm bore size and slotted mounting holes to allow the unit to be located exactly