Just my 2cents......took a class last night, and the instructor told us Coats and Clark now has a coating on it to reduce the "Fluff" issues, and if used a lot in the newer computer machines, the coating can cause the tension discs to freeze up. She recommended aurofil and mettler (neither of which are sold in her shop, so I don't think it was a biased opinion). I have always used mettler....will have to give aurofil a try.