I agree with many of the others, #11 or 12 for piecing and quilting, buy whatever brand your machine recommends, or good quality. I change after about 8 hours of sewing, or if the machine gets noisy.(You can hear a dull needle, it sounds like a loud thunk with each stitch) Beyond that Jo Anns publishes an excellent pamphlet on needles, and uses, it is hard to find at my local store, but has a wealth of information.:)