THESE ARE NOT THE PISTON SEALS. THEY SEAL THE CALIPER HALVES TO EACH OTHER. DO NOT BUY THEM UNLESS YOURS ARE LOST OR LEAKING.
These are the small 0.500″ OD round seals that go between the caliper halves of the 3/S aluminum calipers. Made from heat resistant and brake fluid resistant rubber.
The price is per (1) seal. You need (2) to service one caliper: 1/2-gen front, or 2-gen rear).