4" DuraVent DirectVent Pro Factory Built Double-Wall Chimney Conversion Kit A 46DVA-KCA DuraVent DirectVent Pro Factory Built Double-Wall 4" x 6 5/8" Chimney Conversion Kit A includes: Cap Adaptor and a Retro Connector. DirectVent Pro 4†x 6 5â„8â€Termination Cap and 4†flex are sold separately. Use with 4†x 6 5â„8†direct vent gas stoves. Use existing through the-ceiling wood-stove metal chimney. Route the exhaust gases and intake air through the existing wood-stove metal chimney. 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).