Years ago, oyster shell came as "flakes". We gave it to the hens free choice and never had thin-shelled eggs. Now I can only find oyster shell in pellet form, and the hens don't seem to eat it as much, and we get some thin-shelled eggs. Where do y'all get the "old fashioned" oyster shell??? I've tried all 3 of our feed stores & co-op. Thanks! Wendy