The VBK-E28 Vent Blocker Kit from Middle Atlantic is designed for use with ERK Series racks that are 28" deep. It used to prevent the recirculation of hot air between top-mount fans and nearby vent openings. Vent blockers should be placed over the enclosure's vents located on the upper front of the enclosure and upper sides. This will ensure that heated enclosure air will be forced out through the top-mounted exhaust fans instead of re-circulating, keeping equipment cool.