H.S.S. 4-80 dies are very rare. They are designed to thread 4-80 micro precision threads on rod stock. These threads are used by knife and gun makers to create a maximum adjust threading, or to create a thread that is less prone to "back-out", a common issue with standard coarse threads.
Try a 4-80 thread on your next project and you'll never go back, or back-out again!!!
Die Thread - 4-80
Diameter - 1.0
Fits 1" die handle