4 in Bath Fan Flex Duct Bolt Clamp
A split-ring clamp that holds 4 in (101.6 mm) foil or vinyl flex duct onto a bath exhaust fan collar or wall cap. It replaces the brittle plastic snap clamps that crack and let damp air leak into the ceiling. The ring is 106 mm ID with two grip ridges and a thinned flex zone opposite the split. One M4 x 35 bolt and nut (nut captured in the lug) close the 12 mm gap, so it clamps anything from about 102 to 106 mm OD.
bathroom exhaust-fan flex-duct duct-clamp