These case tubes are made for the new extra large cases and crowns. With crown end diameters of 3.0mm and 3.5mm, you can be sure to find a case tube to fit your watch or crown. There are 12 different case tube options available to choose from, 6 different options with the 3mm crown end diameter and 6 different options with the 3.5mm crown end diameter. These case tubes are made to friction fit into the case. Sizes are listed in the chart below. Made of stainless steel. Sold individually.