I get mine from Quilt Tech - I know they take an L size metal bobbin but I don't know if there is a classification for the height of the bobbin...but I did find that when I bought my Juki TL 2010Q, it came with 100 L plastic bobbins and they did NOT work. The big thing with the Juki is it has to have the little slot for the bobbin winder...I actually interchange my long arm bobbins as my APQS also takes and L with my Juki...I just wind the long arm bobbins on a side winder. LOL