Thread Size: 5/8"-18Set Includes: (1) Taper Tap, (1) Plug Tap, (1) Bottoming TapHigh Speed SteelUse For Creating New Internal ThreadsTaper Taps Have A Chamfer Between 7 To 10 Threads, Commonly Called Starting TapPlug Taps Have A Chamfer Between 3 To 5 Threads, Used As The Second TapBottoming Taps Are Made With Just Enough Chamfer For Starting In The Hole, Only 1 To 2 Threads, Also Know As A Finishing Tap