Wilwood 120-9333 Wilwood Caliper-GM Metric D154 Iron 2.00in Piston 1.00in DiscWilwood 120 9333 Wilwood Caliper GM Metric D154 Iron 2. 00in Piston 1. 00in Disc These are all new and not rebuilt, cast iron calipers, purpose built for racing. Wilwoods GM Metric Calipers are bolt on replacements for 1978 and later GM Metric calipers widely used in "spec" racing categories. Wilwoods new 2. 50 piston GM Metric calipers are now officially approved for IMCA as OEM replacement caliper that meet all rules in Modified, Stock Cars, Hobby