Wilwood Forged Superlite 4R Radial Mount Caliper (120-13232)Forged Superlite 4R Radial Mount Caliper by Wilwood The Superlite 4R caliper series is the benchmark in asphalt short track, late model, modified and open wheel competition. It also enjoys prominence in a variety of road race, rally and sport driving applications. The new FSL4R model series is the latest innovation to this Superlite family of calipers. It has been redesigned with internal fluid ports that eliminate the external fluid cross over tubes.