SmallRig Magic Arm with Dual Ball Heads (1/4"-20 Screws) 3873 is compact and lightweight. Each ball head, 20mm in diameter, features one 1/4 "-20 screw and stretchable pins that prevent twisting. The adjustable thumb lever helps secure ball head at an appropriate angle and comes with a small magnetic wrench at the bottom to tighten the thumbwheels. At both ends of the ball head clamp there are notches which leave more space for flexible adjustment of ball heads as well as accessories mounted thereon. This item weighs only 88g, making it easy to carry around and store.