Fits 3 inch, 4 inch, and 6 inch ducts. IPS SnapCap is a high performance, versatile bathroom, kitchen, and dryer exhaust vent cap. Included is a counterbalanced damper. SnapCap works with any CFM fan and provides a secure connection to 3”, 4” and 6” flexible or rigid duct. SnapCap is available in two constructions: of heavy gauge aluminum and galvanized steel. The IPS SnapCap is the most versatile because one vent fits 3 different sizes, which means less confusion for your roof vent installers.