I bet if you sent an inquiry to Cortland Line Co., they could give you some specs on the "old" way of classify-ing lines and todays equivalents. In 1949, at the age of 13, I got a "casting lesson" from Ted Williams (Red Sox #9) at the old New England Sportsman Show, in Mechanics Hall, Boston. One of the first things he said to me was that I would be better if I had an "HDH" line for my HI, Bamboo Rod. With the innocence of youth, I told him that it took all my "Christmas money and allowances" to pay for the bus ticket and admission so I hoped it would be a bad rest of the winter and maybe I could earn enough shovelling snow to afford the line. When we left the casting pool he marched me over to the Cortland booth, asked for a "HDH" line, handed it to me and told me to follow the care instructions every time I used it and to "Practice, dammit, practice". Said that he would take care of the line with Cortland and for me to "skiedaddle". I will always remember him for that, as much as I will remember his baseball legacy.