HD stands for heavy duty. This is a heavier type of Angel Hair. The material is somewhere between common flash and the original Angel Hair quality. Many times you experience the common flash to be too heavy and the Angel Hair too thin. Voila! The solution was Angel Hair HD. We have longed for this material for a very long time. This material replaces the flash in small flies and the Angel Hair in the bigger ones. This kind also comes in 15 different color blends. You get the whole color chart with the three hot, fluorescent colors as an extra spicy alternative.