This new '477' has been specially developed to replicate as close as possible to the classic Sawyer Bug tying wool. Originally Sawyer used Chadwick 477 and though perfectionists found other substitutes, they simply did not match the original material for color. The Semperfli team had their Chadwick's 477 substitute spec'd to match the original! It comes as a 3 ply, making tying of the nice thick Sawyer Killer Bug a cinch. To perfectly replicate the original Killer Bug simply split the 477 Substitute from 3 ply to one and it matches the diameter of the original 477.