Middle Atlantic GK-4G This GK-4G 4" Protective Gland Grommet (4 Pack) from Middle Atlantic is a pack of (4) rubber grommets, which are designed to protect cabling in your rack or enclosure. In addition to resisting chafing of cables, this grommet's unique design will also block dust and help control airflow within an enclosure. It features a 4 inches design that will work with trade-size electrical knockouts.