The steel cylinders are manufactured at Worthington Cylinder's state of the art facility in Tilbury, Canada. The cylinders are manufactured using the Deep Draw and Ironing (DDI) process. Cylinders start from a circular plate of chrome-moly steel. Multiple draws on a hydraulic press transform the plate into an open ended shell. The shell is then closed, the neck is formed and the threads are machined. The DDI process produces the most consistence wall thickness resulting in the lightest weight, most efficient cylinders. This manufacturing process is what allows us to supply cylinders with the best buoyancy characteristics for scuba diving. During the process of Hot Dip Galvanizing, the exterior of our steel cylinders are submerged into 840°F molten zinc. The process deposits an 8 - 10 mil thick zinc barrier to protect against the corrosive ocean environment. This layer of zinc metallurgically bonds to the steel cylinder. It will not chip and wear away like a painted zinc finish. XS Scuba is so confident that exterior rust will not be an issue, we guarantee it for the life of the cylinder. If the exterior of your XS Scuba HDG steel cylinder rusts, we'll correct it for as long as you own the cylinder, without cost to you. Steel Cylinder Features: Manufacturing Process Built from Chromium Molybdenum steel plates Utilizes the deep drawn process; the preferred method to build a SCUBA steel cylinder This process yields a cylinder with a very uniform wall thickness resulting in a lighter, more efficient cylinder. buoyancy Superior buoyancy characteristics These cylinders have been designed to be slightly negative at the end of a dive Exterior Finish A three-step, rust-preventative process Consists of shotblasting, protective zinc coating, followed by a durable powder coat finish. Interior Finish Highly-resistant to internal rusting Phosphatized interior nitrox Ready Cleaned and sealed at the factory Free of hydrocarbons to a level of 40 mg per square meter Ready for pre-blended nitrox up to 40% FO2 Valves All XS Scuba steel cylinders include the Thermo PRO valve Convertible design allows for standard yoke or 230 bar DIN connections Standard inlet thread (3/4"-14 NPSM) allows upgrade to any other Thermo valve These valves are clean for pre-blended nitrox up to40% FO2 Boots Included with all XS Scuba steel cylinders Quality, self-draining design.