Manfrotto 237HD Flexarm 55cm, 237HD. Flexible arm, diameter: 18mm, 55cm long with hexagon stud to fit Super Clamp 035 with 3/8" female thread and 16mm stud with 1/4" male thread type 18. Specifications: attaches by: 16mm attachment type, attachment (top):, type 18 attachment type, Color: black, diameter: 18, length: 55.0 cm, material: brass, safety payload: 0.5 kg, weight: 0.71 kg