FX O ring dilemma FX Impact

Funshine

Member
Aug 26, 2018
401
29
FL
Deciding to rebuild the Impact X and ran into a snag:
I have a Power plenum on it, and it is the first version for Impact X, Mk II etc. Part number for the o ring shows 5113 20.24 x 2.62 NBR70. However, I am having a hard time coming up with an exact match. I see EPDM o ring for the exact size but no Buna 70 (nbr). For the NBR, I see 20.30 x 2.62. So, my problem is which one should I get to install on the gun. Has anyone changed this o ring, what did you use?
The Mk 3 kits come with the 25.0 x 2.5 size O ring. Except for the above one and the 5.5 x 1.5 nbr70, I have all the other o rings which I had purchased previously.
I thank you all in advance for your assistance as I am a senior going nuts at present.