Frame Clamp for System4This easy to use Frame Clamp is compatible with all Needlework System4 Stands to make a complete needlework system. It allows you to rotate your work 360 degrees to access the back of your canvas without having to loosen any knobs or levers. Lightweight at only 1 pound, the Frame Clamp opens to 1 3 8 and accepts most Stretcher Bars and Hoops on the market. The Clamp holds frames firmly without damaging fabric.