I used these inserts on a square tube project I built and they worked great. The fit was good and snug and the quality was worth the price I paid. In my particular case I used 3/4" square metal tubing and .065 gauge. I think you could easily use these plugs for other gauges of metal as the ribs on the plugs have a crease to allow for bending. if they are attached I would definitely order these parts again.