Yongli YL-ZJ series laser tube brackets suitable for all models of CO2 glass laser  tubes, due to the adjustable inner diameter and holding hights. To assist our customer install the CO2 laser tubes properly, we put scales on the side of YL-ZJ Laser Tube Support. Kind Reminder: To properly install a CO2 Laser Tube onto your machine, you have to make sure the laser tubes are horizontally placed. And also, the laser tube is holded firmly. So that you can get a high quality beam alignment.