These case tubes are made for the newer extra large watch cases and crowns. With crown end diameters of 3.0mm and 3.5mm, you will be sure to find a case tube to fit your watch and crown. This kit includes 12 case tube options including 6 variations of the 3.0mm crown end, and 6 variations of the 3.5 mm crown end. These case tubes are made to friction fit into the case. Sizes are listed in the chart below. Kit has 12 pieces. Made of stainless steel. Refills are available.