Holds 3/8" stem and dovetail. Noga unique central locking mechanism with spring loaded bearing Powerful 176 lbs. on/off magnetic base with fine adjustment. Bottom arm length: 4.33" Top arm length: 3.98" WARNING: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.