HC-6437-010.. Rectangular Vent Grommet in White Nylon. These grommets are often used to ventilate cabinets where computers, music systems or other electrical components which create heat in an enclosed space. 4-1/4″ long x 3-1/4″ high. Designed to fit a 5/8 inch to 7/8 inch thick wall. Walls over 5/8 inch thick may require a small amount of glue to keep 2 pieces together. Sold by each.