3/8 X 24 Auto Pro50 Thread Chaser Construction and Industrial Construction and Industrial 3/8 x 24 The best and easiest tool ever made. The greatest time saver, since sliced bread The pro50 Chaseemback tools are made of a 60 Rockwell hardness Wrap around the good threads, chase threads in either direction, up or down Check out the rest......and buy the best. Save time, make money.