4" Type B Gas Vent Tee Cap 4GVTC This tee cap is used to cover standard tee or increaser tee. Remove tee cap to inspect the system; clean out debris or collected condensate from the common vent. Fits on inner liner. For Category 1 gas appliances 1" clearance to combustibles Easy-fit twist-lock design with no fitting hassles 0.012" aluminum inner 0.018" galvanized outer