I think the smaller of the two fittings takes the 7/16 x 5/16. I think the larger one may be 1/2" OD. I bought a kit from Oriley's labeled "Quick Disconnect" oring kit. Quick Disconnect was the brand name (go figure). It comes with 2 3/8 x 1/4 and 2 7/16 x 5/16 rings. The larger rings appear to be the right size for the smaller quick disconnect fitting (return line). I just need to find the ones for the larger fitting