High-performance replacement piston designed specifically for StopTech ST-40 brake calipers. This 36mm piston is manufactured from high-quality materials to ensure thermal stability and resistance to corrosion under extreme track and street conditions. Compatible with various Big Brake Kits (BBK) utilizing the ST-40 housing. Related components and service kits: - 36mm Dust Boot: 143.99036 - 36mm Pressure Seal: 143.98036 - ST-40 Rebuild Kit (Single Piston): 143.99136 - StopTech Brake Fluid (STR-600): 501.00001 Note: For a full caliper rebuild, check the specific piston configuration of your ST-40 kit (pistons may vary in size within one caliper).