I realize that axyto indicated "Viton 112" is the manufacturer specified o-ring.
Was this mentioned in the owner's manual or the official tech repair manual?
Or was this info given out by cerich (owner of HOG) here on ScubaBoard?
I wonder whether anyone has tried the -111 o-ring size. The -111 is slightly smaller than the -112. Obviously, this all depends on the dimensions of the DIN o-ring groove on the HOG D1 first stage. Material (Buna-N, Viton, EPDM) of the o-ring really shouldn't affect the fit of the o-ring, per se. Is it possible that durometer (hardness) of the o-ring could be an issue?
I've never had a DIN o-ring pop out of any of my Apeks first stages. Am I just lucky?