On Monday, June 8, 2020 at 9:38:29 AM UTC-4, wrote:
Also note that the small hookup ring can wear. If it gets deformed or reduced in size, it can jam or prematurely release. I looked for the specification on minimum thickness, but couldn't find it with a (very brief) search. Check with Wings & Wheels to see if they know the correct "go-no go" dimension.

Mark - according the the DIN-LN65091, the oval ring has a wire diameter of 8mm, +0, -0.3mm. The round ring has a wire diameter of 7mm, +0, -0.3mm. The O.D. of the round ring is 35mm, +-0.3mm, which would give it a nominal I.D.. of 21mm. If you do a quick tolerance stack-up using just min.-max. material conditions while neglecting any ovality, the I.D. could range from 21.9mm to 20.7mm
The material specifications call for a high carbon Chrome-Vanadium alloy. No welding is permitted.

Uli
'AS'