Metalbest 4DT AJ12 Direct Vent Black Vent Pipe Pipe Length 4" x 6 5 8" Direct Vent 4" to 10" Adjustable Length Pipe from Direct TempPipe lengths provide the core part of the chimney system Pipes should match the inside diameter of all other pieces and all pieces should be from the same manufacturer This adjustable length slides onto a standard pipe section for adjustment from 4" to 10" Direct Temp system features stainless steel inner and heavy duty galvanized steel outer walls Heavy duty centering brackets keep inner pipe centered and chamfered edges allow for easy slide together assembly The free floating inner liner allows the pipe to expand and contract under high temperature without creating gaps or stress points The LockTab(r) is a unique design that allows for 360 rotation while securely locking the sections of pipe together with just a push of the tab Features:Siliconized fiberglass sealLockTab securityPipe rotates easily to align system componentsNo sealant requiredHigh efficiency performanceConnection Specifications:Adjustment from 4" to 10" lengthJoint Connection Type: Twist Lock standard on all diametersMaterial Specifications:Outer Wall: Heavy duty galvanized steelInner Wall: 304 Stainless Steel