We are told the thread industry utilizes the ‘denier’ designation for sizing and strength. The 3/0 to 14/0 ‘aught’ thread labels that many of us have used here in the U.S. and beyond are reportedly going away.

All well and good, as long as there are comparison charts during the transition from ‘aught’ to ‘denier’. There already is great variety in tying threads around the world. In my little corner, I/you will eventually figure out the four + sizes of thread, I require and we will move on.

Threads (Aught vs. Denier) Fly Tying World Blogspot