4" DuraVent 4" X 35'/3" X 35' Conversion Kit 46DVA-CL34P This masonry chimney conversion kit with Flex and High Wind Cap is used when installing a direct vent co-linear insert into a masonry chimney. The kit includes a high-wind termination cap to protect your chimney from debris and water entering and two pieces of aluminum flex lengths - one Red (exhaust) and one Green (air intake). 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).