Manfrotto Panel Clamp w/5/8" Socket, Attaches to Round or Square Tubes This Manfrotto Panel Clamp is designed to attach onto round and square tubes from Ø 22 mm to 30 mm. Ideal for supporting reflector panels or hanging objects from pipes. This replaces the Manfrotto 2974. Attachment (bottom): 16mm; clamp range - max. (round tube): 1.18 in clamp range - min (round tube): 0.87 in.; color: black; material: aluminum; weight: 0.64 lbs.