Crosman 1701 fill adapter inside o-ring size?

Can anyone tell me the size of the o-ring on the nipple adapter inside a 1701 fill adapter? It is part of an assembly shown as number 35C on the parts diagram without any additional information. Here is a picture of what I’m asking about. Thanks!


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Crosman generally uses a -006 on the check valve but I haven’t worked on a 1701 so you may want to wait for confirmation.

If you take it off and measure it with calipers, the OD would be very close to 0.254in (quarter inch), or perhaps a few thousandths smaller if it has lost some material due to abrasion.

Go with a 90 durometer replacement for best longevity.