All, some people use a lighter weight thread in their bobbins. A couple that I have used are from Superior Threads: So Fine, this is a 50wt but is finer than the 50wts we use to piece with and Bottom Line which is a 60wt. Both of these are Polyester so in case that bothers you - it doesn't me and the So Fine doesn't look like a poly. I have a long arm and use it in my bobbins most of the time.