5” VG AL29-4C Stainless Steel Tee Cap Ventinox VG Liner is a gas and vaportight lining system designed to meet the challenges of venting the new generation of energy-efficient oil and gas appliances. Because combustion is so complete and very little heat is lost into the flues from these new appliances, flue gases are cool and saturated with water. Water condensing inside the flues combines with soot to form acids, which can seriously damage the entire chimney structure. Because VG is nonporous, leakproof, and can be insulated, its ideal for reducing and containing the flue condensation.5” VG AL29-4C Stainless Steel Tee Cap The Tee Cap is used to seal the bottom of a tee. Removing the cap allows for the cleaning of the system.