before you need one, take the o-ring off and go to Ace Hardware, and match it to the ones they have.They have various sizes,in a sectioned box. Buy a couple 3 of them, to have. I was unable to come up with one from Remington one time, and was forced to use one it works just dandy, in fact it's probably the one thats still in it. They are dimensionaly the same, and the material seems a little more resistant to oil or solvent.