Yes, you use tin snips or wire cutters to cut off the excess and, of course, once sealed (closed) they cannot be opened so, you have to cut them to remove them and, once cut, they are useless. I use them because my DH is a truck driver so, he can ask for a couple of extra seals from customers that use them and, for us those are free but, I have bought them when I needed more than I had on hand. Flying J, TA, Pilot and Petro truck stops always have them and, most independent truck stops as well. Some Loves and Kwick Trips have them but not all because those are usually just fuel stops and not a full service truck stop (one that has showers, a restaurant and/or a repair shop) Most full truck stops will have the metal seals.