Where does the "O" ring go?

[scout4bta]

Finely getting around to doing front axle inspection on the new to me GW after a year of driving.
Have found a single O ring on the ground after pulling the pins on the calipers on each side. You think I would have looked for it when I went to the other side, but no.
The O ring is about 1/8" thick, just fits over the pins. Why just one? Is the PO messing with me?

[babywag]

All GM type calipers (should) have them installed inside each caliper casting "ear" they surround the pin holes.
A big one and a little one per caliper.
Almost nobody knows they exist or ever replaces them!
They should be lubed w/ good brake grease as well.
They're a consumable anytime a brake job is done should be replaced.

Any autoparts store will have kits that include them.

[scout4bta]

Thanks babywag.

[scout4bta]

Question about the O rings, what's their purpose?

[babywag]

stabilize calipers pins & sliders, reduce brake noise, etc

[scout4bta]

At Autozone: Duralast Brake Disc Hardware Kit H5500, $4.19.