Material: zinc alloy It is not a high-quality material and is not recommended for long-term wear as a cock ring. It is only recommended as a measuring ring. Sold by set,1 set contain 4 rings(4 sizes,1 ring for each size)You need to fill the sizes you want in the text box when place order.For example,40,42.5,45,47.5mm. Some ring thickness is 5,mostly 6mm,some ring thickness is 8mm. Available inner diameter of ring is 24,26,28,30,32,35,38,40,42.5,45,47,5,50,52.5,55,58,60,62,68,70,74,78mm. This various size ring can be used as sizing ring for customer who want to custom a chastity cage but not sure which size would be the best.So spending a little money to buy some different sizes cock ring before spending much money to custom a chastity cage without correct base ring size,it would be a better solution.