Nano Silk is regarded as the tying thread choice of professional fly yers world wide. Being so super strong and available in such a variety of colors and Deniers it has endless possibilities and can be used for micro to medium flies. Virtually unbreakable and still capable of being split down for dubbing twists there is no fly tying thread as stong as Nano Silk anywhere.With Nano Silk you will have confidence that even the smallest of flies can be tied without your thread breaking!Breaking Strains 1,9000gm / 4.2lb strongest in test