The set contains 4 flexible rings ranging in size from 0.4 to 0.75 in. unstretched. The rings are easy to place and remove even with slippery hands because each tab features a thick border allowing the rings to be adjusted with ease. The set is made of non-phthalate TPR. Ring sizes: small 0.4 in. inside diameter (ID) stretches up to 2 in.; medium 0.5 ID stretches up to 2.5 in.; large 0.6 in. ID stretches up to 3 in.; extra large 0.9 in. ID stretches up to 3.5 in.