We have had many calls for larger snap-on nylon dies to fit our CRY-905.00. This set is designed for larger oversized watches that are very popular and most have snap-on case backs. There are a total of six pieces three flat on both sides 35 40 and 45mm and three double sided concave that are 40/42.5 45/47.5 and 50/52.5mm concave.