Museo Alu-Frame Aluminum Stretcher Bars feature a reinforced structure comprised of wear-resistant aluminum and sturdy wood for maximum stability. Unlike all-wood stretcher bars, aluminum bars are unaffected by changes in humidity and temperature. They won't twist, bend, or warp. - MUSEO ALU-Frame Aluminum Stretcher Bars and Parts - Basic Assembly KitMuseo Aluminum Stretch Bar, SET 1 - This kit contains all the pieces required to assemble a non-braced frame. It includes four corner connectors, one stretcher (for keying the canvas), two screw eyelets, and one Allen key. You need one Assembly Kit for each frame you build.To build the frame, slip a stretcher onto either end of a corner connector and tighten the screw with the Allen key until you reach your desired tightness. Repeat the process at the other three corners. Use the screw eyelets for easy hanging. Screw them into the frame and string a hanging wire (sold separately) between them. These hangers are recommended for works smaller than 72" × 72".