Dreaded 2016 CX-5 Rear Caliper Piston pushed out too far - what is this ring part?!

[zacscott77]

I made the dreaded mistake of activating Maintenance Mode aftet the rear calipers were off, thereby pushing the pistons out too far. This, in turn, ripped both rubber boots around the pistons on both sides, leaking brake fluid. I took off the rubber boots and took the pistons out for a possible rebuild. I know I have to take the ESB off to screw the pistons back in, but something came up that I haven't seen addressed. When I took the pistons out, a little loose metal open ring (not sure what to call it) came out on both sides. The ring is open on one side with a slight protrusion. Where is this supposed to go during the rebuild? Help! Pic attached.

 

[erhayes]

Goggle a picture of the caliper assembly.

 

[stickerbush]

Parts fiche does not show anything like what's in your photo. It looks like it's a retaining clip, but no idea where it might go. Seems like it would be obvious looking inside the caliper bore with the piston out.