This summer I went to change the sewer valves on our RV. Bought the new valve assemblies and got right to it. Promptly dropped one of the o-rings in the grass. Searched and searched on my hands and knees for an hour, took my clothes off, took my boots off.... Nope, no o-ring. Went back to the store and had to buy a whole new valve assembly because they don't sell the o-rings separately. Guess what I did when I got home. Dropped the new o-ring in the grass.....