The Propane Gas Cylinder Y Tee Piece - POL , allows two regulators or couplings to be fitted to a cylinder of gas. Can also be used in conjunction with Gas Pigtails to link propane cylinders together to improve the gas supply. This is particularly important with the use of heaters and other large appliances that need two or more cylinders, e.g. Marquee heaters, space heaters, etc. Male POL x Female POL x Female POL.