4" DuraVent DirectVent Pro Small Vinyl Siding Standoff Kit 46DVA-VSKS This vinyl siding standoff kit is used as a heat shield on structures with vinyl siding or other temperature sensitive materials to help prevent warping and/or melting of the material. Use only on horizontal terminations and on any irregular surfaced siding (i.e.: ship lag siding shake shingle siding) so cap is not imbedded in the siding. Kit includes 4-pieces;sized for Sconce Cap Round Horizontal Cap and H2 Horizontal Cap only. 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).