Unicyl Unvented S. Steel Indirect Cylinder 250L. This cylinder has been developed using Duplex Stainless Steel as it offers a much higher level of strength and a lower carbon content in comparison to glass lined mild steel or lesser grades of stainless steel. This makes the cylinder much lighter, and better equipped for resisting all forms of corrosion. Completed with a protective finish, this cylinder safeguards against all premature corrosion, resulting in this cylinder having an excellent working life.