Like in that groove above the threads? I got a hardware kit that came with only the orings for the slide and other end (4small 4big). I have to finish this brake job and see if I can get them somewhere close. I'm not home so this is a PITA.
It's not on the car and not on the diagram at the Chevy dealer here, so F it. Must be a groove for another GM caliper type or something. Brakes feel good too.
