In Reply to: Re: NAA piston pump O-rings choice posted by Ed Gooding (VA) on January 27, 2024 at 06:50:45:
According to Messicks parts page the o-rings are standard AS568 o-rings. Dash size and hardness:
-214, 70 durometer for pressure
-216, 70 durometer for suction
You can get them in round, square, or X profile.
TOH