I recently acquired a Brother SE350 and have been trying what threads I already had. I had no luck with the rayon embroidery thread. It kept shredding on me, but it was old. It had been cheap thread purchased at WM several years ago and that may have had a lot to do with it. I do know that keeping it in the frig helps, but I don't have enough room for that. Have had good luck with the polyester. Have a lot to learn about my machine & no one around to help me out. Good luck.