Made of quality tool steel. Shanks are precisely ground. Much precise and accurate design with option of holding 4 imperial size round threading dies. It can hold 13/16", 1-5/16", 1" & 1-1/2" round dies, through 4 holders (2 on each size of the main bodies that floats on the parallel shank). Sizes are laser marked on each holder for easy reference of the end user. The morse taper goes inside your lathe's tailstock taper & the body of the holder having threading die floats on the parallel part of the shank while creating threads on the round work piece hold in the lathe machine.