The Broan-NuTone 641 Aluminum Wall Cap is a robust, easy-to-install vent for exhaust fans (bathroom, range hood, rec room, home gym, etc.). This cap provides reliable ventilation and features both a back draft damper and welded bird screen, preventing outside air from entering the home or birds and small pests from entering duct work. The back draft damper is spring loaded and features a padded damper zone, which reduce noise from wind induced chatter. Compatible with 6" ducting. Not suitable for dryer venting.