I have stayed away from pre-wound bobbins because I bought a package at a quilt show once and it was worthless. There were 6 bobbins and the thread broke in my hands in all 6. Since it was a vendor at a show I was not able to return it and I couldn't even use the thread to baste a quilt because it broke so easy when pulling it thru the fabric. My sister bought some too and had the same problem.
So know where you buy it so if the thread is bad you can return it.