6 different sizes per set of your choice to meet your needs. Made of bearing steel. It has high and uniform hardness and wear resistance, and high elastic limit, your good helper for work and life. The flares will always have the same size and will fit perfectly; The swages present a perfect depth and a tight fitting, that will make the brazing easier, reducing the fatigue stress over the coupling area. A full range of forging tools makes it easy to expand HVAC tubing, the forging plug will provide a large exchange depth for a perfect fit. When the air conditioner is installed, expand the copper tube, make two mutual copper tubes. (To be installed in manual electric drill).