Williams AV BKT 024 Wall/Ceiling IR Mounting Bracket (Black)Omnidirectional wall or ceiling mounting bracket. Use with IR E4 and IR T2. Specifications Base 1 2 (50. 8 mm) round base with four 0. 188 (4. 8mm) holes on 1. 6 (40. 6mm) bolt circle for solid surface mounting Base 2 T Bar Clip for drop ceiling rails Base Cover Black Vinyl, covers either base Shafts Two 0. 5 (12. 7mm) diameter, 2 (50. 8mm long aluminum, black. 1 4 20 stud with lock ring. Head 190 Tilt, 360 Turn [&] 360 Rotation Finished Lengths 2, 4