The Matthews Matthellini 6" End Jaw Grip (Silver) provides strong, solid gripping of round, square, or rectangular tubing and many other common and irregular shapes. The End Jaw has the fixed jaw mounted at the end of the threaded portion of the shaft. Includes a Baby (5/8") Pin for mounting fixtures or other grip items.
 
https://www.bhphotovideo.com/c/product/301945-REG/Matthews_420210_Matthelini_Grip_6_End.html