Yellow Dot Embroidery Bobbin Case For Janome MC15000, 12000, 9900, Elna EL900 & EL860 The yellow dot bobbin case has twice the amount of tension as the standard bobbin case (red mark). You can use this bobbin case whenever the bobbin thread is finer than the needle thread, to prevent the bobbin thread from slipping to the top of the work. During normal embroidery, if the bobbin thread is not Janome blister packed pre-wound, it is recommended that you use the high tension bobbin case (yellow dot). Use the standard (red marked) bobbin case when sewing lace designs or quilting in the hoop. For use with: Janome MC15000, MC12000, MC9900 Horizon, Elna EL900 eXpressive, EL860 eXpressive