4" Junction box mounts on panel to allow them be daisy chained together on the same switch (4-in / 4-out) Compatible Luminaires: NCSP-22: 2'x2' Contractor Series Backlit Panel with Selectable Lumens & CCT NCSP-24: 2'x4' Contractor Series Backlit Panel with Selectable Lumens & CCT NPDBL-E22: 2'x2' Backlit Panel NPDBL-E24: 2'x4' Backlit Panel NPDBLSW-E22: 2'x2' Backlit Panel with Selectable Lumens & CCT NPDBLSW-E24: 2'x4' Backlit Panel with Selectable Lumens & CCT NPTCB-E22: 2'x2' Troffer NPTCB-E24: 2'x4' Troffer