Five Oceans Marine Low Profile Cowl Vent, 3", 4" This durable and flexible unit has soft-white and red interior PVC COWL VENT ALLOWS proper ventilation to help prevent mold and mildew and keep your boat fresh with no use of power GREAT for bilge ventilation with or without a blower. Includes Snap-on Deck Plate and cover DESIGNED to withstand harsh marine environments CUTOUT size is 3 1/2" and the height above deck is 3 5/8". Material: Flexible PVC Size: 3&#034; Cutout Size: 3 1/2&#034; Diameter Height above deck: 3 5/8&#034;