These AFCO Brake Pads fit in a metric GM style caliper. The SR32 compound was developed for the right fronts of dirt cars where low grip is needed to help build bias in the front brake system and help the car turn better when you have to use 4 wheel brakes. The SR33 compound was developed for improved stopping power over the standard C1 compound and has a wider temperature range that will reduce brake fade. The compound is made for the front and rear of dirt cars and rear asphalt cars where a medium grip pad is needed. The SR34 compound was developed for improved stopping power over the standard C2 compound for rear dirt cars and front asphalt cars.