Keystone Vessel UN Hazardous Materials KSC40L KSC450B Electronical Grade Gas Cylinders Got US DOT APPROVAL Keystone Vessel UN Hazardous Materials KSC40L KSC450B Electronical Grade Gas Cylinders Got US DOT APPROVAL authorized to manufacture the following specification cylinders UN ISO 18172-1 and UN ISO 21172-1 drawing numbers: KSC40L-00, Rev. 1, UNISO 18172-1:2007 and KSC450B-00, Rev. 1, UNISO 21172-1:2015 by the Gas Metal Arc Weld manufacturing method, at the facility located at the address above, under the supervision of the Independent Inspection Agency identified under section 5 (b) of this approval.