4" DuraVent DirectVent Pro Round Horizontal Termination Cap 46DVA-HRCS Use for through-the-wall termination. Check installation instructions for restrictions on horizontal cap terminations such as minimum distance from windows and doors. Available in aluminum only. Check with appliance manufacturer for approval. 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 Unitized concentric construction. Inner: Laser-welded super-ferritic stainless steel .012†Outer: Laser-welded paintable galvalume .018†Silicone O-ring seals on inner liner and outer wall Precision twist-lock connection on outer wall