Calipers- Uses common 7/16-20 SAE thread fluid inlet for larger brake hose compatibility. Caliper features low-drag piston seal and piston dust seal for long life/street use. Available as left or right side casting, only buy what you need for service/repairs. Uses commonly found FMSI D154 reference number disc brake pads. No core charge required and no need to ship your old calipers back. Designed for 1.00-inch thick disc brake rotors (can fit .810-inch rotor with pad spacer) Uses 5-1/2-inch bolt spacing mounting pattern. Brake pads, brake hoses, and caliper slide bolts sold separately. Stop Effectively with Our IMCA Approved GM Metric Disc Brake Calipers Spec class racing removes a lot of the “wallet racing” by equalizing the racing equipment and focusing on the racer's abilities. Having rules that specify specific parts, weights, dimensions, and more means everyone, theoretically, is running the same car with the same performance, making the race more about driver skill and race strategy. It is a great, cost effective, way to go racing while being competitive and having some fun. One such spec item the IMCA mandates for many of their racing classes, including Modifieds, Hobby Stock, and others, is the use of the '78-'88 GM Metric caliper. Having the same caliper body and piston size as an approved IMCA part means everyone has the same braking system capability. The issue has been finding a good GM Metric caliper though. Parts store remans are iffy at best, often being remanufactured with substandard parts, and requiring core charges or turning in your old calipers. We opted to craft a brand new reproduction steel brake caliper that meets all the class rules for IMCA approval but can also be used on the street with any aftermarket brake system that specs these GM Metric calipers for their brake kit