We have a number of shells to pass along that we were never able to use (we went a little crazy buying these for our guys and they had a surplus). There are a variety of sizes, both D and round openings, clean and boiled briefly for sterilization (which is what we had done for our guys and they all remained very healthy). Shells vary in size and are mostly between 3/4" - 2" (total size) with openings between 1/2" - 1.25".