What do you need it for? If you have a filter with a waterfall style return, airstones are only decorative, not needed for areation. For just normal areation in a small tank, anything on Big Al's will do. (The very cheap stones will sometimes fall apart, but I don't see those on the site.) My personal tank has a bubble wall accross the back, as I'm running a low-tech tank and the bubble wall is my primary method of water circulation.