HC-6437-021... Sold by the Each. Grey Plastic Rectangular Vent Grommet, 2 piece grommet to sandwich the wood. Has very small radius corners. Vent fits a 4-1/4" x 3-1/4" hole and is 5/8" deep. Flange is about 1/4". Vents are slightly angled so air can be directed up or down depending on position it is installed. Vent thickness can be adjusted 5/8" to 1" thick material but may require glue for install.