Front Left Chrome Differential Bore 6-Piston Caliper (0051-2915-CH) by Performance Machine®. Differential bore technology has been applied to this 6-piston version making it the most powerful and stylish brake available for new generation bikes. PM Brake Systems have set standards in the industry for braking. Style and function merge for an ultra-clean look with proven technology for optimal braking performance. Each caliper is machined from billet aluminum to eliminate flex. Subjected to rigorous testing on the PM brake dyno to ensure performance.