In Reply to: NAA piston pump O-rings choice posted by BlasterStumps on January 26, 2024 at 10:16:52:
JUST8Ns sells a hydraulic manifold O-RING kit --- SEE LINK if this helps.
MPC shows O-RING p/n EAF-990 as well.
If you have your old O-RING, you can measure the ID, OD, and diameter of ring with dial calipers and find a match from any supplier. Try McMaster-Carr:
https://www.mcmaster.com/products/o-rings/
Tim Daley (MI)