Description:Made of metal materials, durableWith standard 1/4"-20 through hole design, suitable for the camera and magic arm which needs connect each other with 1/4” screw hole.Total length/height: 17mm (measured by hand, may be a little more or less)Outer diameter: 20mm Package Include:1 x 1/4" to 3/8"(or 1/4" to 1/4") screw adapter