Mounts on any column with 3/8” thread, this side arm allows positioning of two heads on a 90Degree perpendicular angle. Two positional head mounts on the side arm allowing the possible mounting of four heads. This replaces the Manfrotto 3153B. Column travel: 12.09 in.; attachment: 3/8'' screw ; attachment (bottom): 3/8- Inch female thread; attachment number: 4; color: black; length: 23.62 in.; material: aluminum;