I wanted a new breech seal for an old Diana rifle. I took the old seal to Home Depot I think (maybe Lowe's) and in the plumbing department they had blister packs of breech seals, only they called them plumbing O rings. I have no idea how they could make such a mistake. Anyhow I picked up a pack of the correct size matched to my seal and was on my way. Ace Hardware would probably have had the correct size as well.