rear axle seal question

[narfire]

I have noticed the past little while oil on the inside of my rear wheels/rims. Not brake fluid but gear oil. While changing rear calipers,I pulled the axle and the "O" ring is shot. I pulled the seal as well. Wondering if there was a gasket between the axle housing and the brake caliper bracket,two metal surfaces? Is that an "O" ring that can be bought at napa from their selection or special order.Also the rear seal looks the same as a cam or aux. shaft seal, are they the same?(I have a few spares and would look tomorow)
Any ideas what might cause the O ring to get bent outa shape. The other side is fine,no issues.
Thanks people,hope you had a good top down day.
Chris

[So Cal Mark]

the o-ring seals the outside of the bearing to the housing. It's a hard one to find since the diameter is so small for a large o-ring. The axle seal is not the same as the cam seal

[pope]

I picked a couple of outer diff. bearing O-rings from IAP for $3 each.

[narfire]

Thanks, I'll order parts Monday.
Wondering though why the O ring was screwed up in the first place? Outer race of the bearing turned and ground the O ring?