Tech Lighting FreeJack Port Alone Minimal 1 1/2" diameter, 2 1/2" deep. Can be installed in a range of locations. Access to back of ceiling is not needed. InstallationMounts to Tech Lighting's special cylindrical 1 1/2" diameter, 2 1/2" deep junction box (included). If wall mounting, head should be no longer than 6". NOTEFor use with remote transformer and any FreeJack pendant or head (sold separately).