Gas Vent Pipe Adapter; Type Double Wall, Gas Vent, Round to Oval; Applicable Standard UL 441, CUL, NFPA 54/211; Size 4" Round to 4" Oval; Length 8.75"; Material Thickness 0.012" Inner Wall, 0.018" Outer Wall; Material Aluminum Alloy Inner Wall, G90 Galvanized Steel Outer Wall; Locking Connection Type Push-Tab Lock; Used On Gas Vent, Oval Pipe; Warranty 1 Year Limited