FSLI4 and FSLI4/ST calipers provide the pad wear performance advantages of differential bore pistons with the option for ultimate heat protection using Thermlock® pistons in the ST models. Differential piston bores compensate for leading-edge mechanical loading and temperature variances across the pad face to reduce pad taper wear in sustained high temperature applications. Thermlock® pistons in the ST models block heat transfer from the pads and reduce temperatures in the caliper, fluid, and seals by up to 25% over standard stainless steel pistons. These are the go-to calipers for all types sustained hard braking on dirt and asphalt ovals and a wide range of off-road, rally and road course applications.Pit Stop USA offers Wilwood Forged Superlite Internal 4 Caliper w/ Thermlock Pistons - 1.88", 1.75" Piston Diameter, 1.250" Rotor Thickness - LH Rear Side Mount 120-11332 at low everyday prices. Be sure to check out all of our products from Wilwood Engineering including Wilwood Engineering Forged Superlite.