4 Medium Size Hermit Crab Changing ShellsSize Range: 1” – 2” (25-50mm)Opening Range: 5/8” – 1 1/2” (15-35mm)Great for Small to Medium Sizes Hermit Crabs. Shells include select Turbo Shells with clean and smooth round Openings, plus a pair of Fairyland Snail Shell with large D-shaped openings. All Natural Seashells, Aquarium Safe.