It all depends on the look I want to accomplish. I have an HQ16. Most often I use Maxi-Lock serger thread. If I want a heavier thread I mostly use King Tut. I prefer to use a thin thread because of backtracking, fine stippling or small background fill. Most of the time I do use the same thread in the bobbin and needle. I also use the Super Bob's from Superior. I also use trilobal poly machine embroidery threads.