The Mega Slim will fasten from 1-1/4in pipe (1.66 OD) to 2.050 OD Truss Tube. It has a wide wing nut for easy fastening of the coupler to the pipe or tube as well as a hex pocket for 3/8in bolt. includes 3/8in×1in zinc plated bolt with nylock nut and spring washer. The bolt fits flush into the Coupler.