I'm sure there is a little pile of these things hiding somewhere in my garage.
When I started rebuilding the Sunbeam, I had the head upside down on the bench with valves, springs etc fitted. I just moved it slightly and both exhaust collets popped out! If it had happened when the engine was running it would have been expensive.
Model 10 spares being rather elusive I turned a new pair up out of an old metric HT bolt I had lying about.
