In Jerry Howell's drawings for the Farm Boy, he specs this for the piston o-ring
"piston ring groove .105" wide by .110" deep for a .094" section by 1" diameter Buna-N "O" ring."
I've checked all of the usual suspects (McMaster, Grainger, O-rings-R-Us, etc) and no one has an.094 O-ring.
I got these two sizes from McMaster:
.070 thickness, .864 ID, 1.004 OD
and
.103 thickness, .799 ID, 1.005 OD
Any reason to use one over the other? I've held off machining the o-ring groove until the general wisdom here has been heard from.
BTW, if anyone needs either of these sizes, I now have 100 of each. Just ask.