Check the listing for details. Middle Atlantic MAPI VBK-BGR Magnetized Vent Blocker Kit. Condition: Open box, Made in United States. Listed at 9.99 USD. Compatible with BGR Series enclosures. The VBK-BGR features vent blockers are 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, upper sides, and upper rear door (depending on enclosure).