SRAM Maven Bronze Disc Brake Caliper Assembly - Front/Rear Post Mount 4-Piston Dark Polar A1SRAM Maven Bronze Disc Brake Caliper Assembly Front Rear Post Mount 4 Piston Dark Polar A1. Modern mountain bikes have redefined what riders are capable of pushing the requirements forheavy duty power further than ever before. Maven is SRAMs answer to that evolution with monstrous 18 and 19 millimeter pistons driving 50% more power than Code. 2 Piece forged aluminum caliper features 18 and 19. 5 millimeter pistons for best in class power Stiff 4