4" DuraVent DirectVent Pro Black 11" - 17" Adjustable Pipe 46DVA-17TAB This adjustable pipe adds length to your DirectVent pipe. Use of sealant is optional unless specified by the appliance manufacturer. Provides combustion air and exhaust venting for gas appliances Clearance to combustibles mandated by appliance listing The components twist-lock together for a quick secure fastener-free installation 0.020" aluminum inner 0.018" steel outer Offsets venting obstructions .020†aluminum inner wall .018†galvanized steel outer wall Painted outer walls made of laser welded .018†galvalume steel. Caps also available in stainless steel and copper. Outer pipe brings combustion air to the appliance. Inner pipe exhausts flue gases to the outside. Gaskets or sealants not required (unless specified by the appliance manufacturer).