4" DuraVent DirectVent Pro Small Wall-Pass-Through Wall Thimble 46DVA-WTS This wall thimble provides a complete wall-pass-through and firestop. Use with Round Horizontal Cap Sconce Cap and H2 Horizontal Cap only. May be required in Canada. Refer to the appliance manufacturer's installation instructions for requirements. 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).