In measuring for a new Oring, do you measure from the inside, outside or middle? I'm looking at my water filter and need a new ring. The ring is about 4" but 1/8" thick. So that would be about .25 ...
I have always just taken in my old o-ring to Home Depot and found a perfect match... But, these guys have every 0-ring under the sun listed by filter name and manufacturer....