SmallRig Magic Arm with Dual Ball Heads (1/4”-20 Screw and NATO Clamp) 3875 is compact and lightweight. Both ball heads are 20mm in diameter, in which, one features a 1/4 "-20 screw and stretchable pins that prevent twisting, and another has a NATO clamp that supports the cage, top plate, etc. with a NATO rail. 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 that leave more space for flexible adjustment of ball heads as well as accessories mounted thereon. This item weighs only 91g, making it easy to carry around and store.