I have used prewound bobbins with cardboard (plastic does not work in any of my machines for some reason) with success in both my DSMs and my shortarm (I sold it recently). I have quite a collection of prewound bobbins with beautiful thread colors from Superior Threads. When I bought my Bailey LA, I found it uses Class 15 bobbins. Not to worry! I simply use the bobbin winder to transfer the thread from the L bobbins to Class 15 bobbins as needed for any project on hand.