I piece with mettler cotton. It runs smoothly through my machines. I use superior and fil-tec on my long arms, so I would imagine they would work for piecing too. The big difference in the big brands is how the thread is wound on the spool, or how it comes off the spool. I know it sounds crazy but it can make a big difference. I would avoid any thread that is sold on a giant cone at a price too good to be true. Also read your spool carefully, make sure it is not a blend. It's like batting, it says cotton but at closer reading it's a poly cotton blend.