Z-Flex Z-Vent 4" Termination Box with 4" Sleeve Stainless Steel (2SVSRTF04) 4" Vent Termination Box with 4" Sleeve Stainless Steel Venting Can be used as either an intake or an exhaust piece Has a bird screen to keep animals out of your exhaust system. Rated AL29-4C and is approved for Category I (vertical only), II, III & IV applications Contains a built-in, fail-safe gasket and locking band connection