This is a pair of genuine GM part number 15765071 “Spring Isolators”.
Fits all SSRs 2003-2006.
This Spring Isolator mounts between the top of the rear coil spring and the spring mounting pad on the frame. It is intended to eliminate the transmission of noise from the rear suspension into the truck frame.
These are priced and sold only as a PAIR. An order of “ONE” pair will send two isolators to you.