This set of 12 Class 15J transparent plastic bobbins is for use in Singer Futura Embroidery Machines series 2600s, 3900s, 7400s, 8700s and Izek 1500 sewing machines. The bobbins come in a plastic storage box, which is reusable and easy to store. Consult your sewing machine’s manual to ensure correct bobbin size. Use the transparent bobbins beneath the needle plate in automatic sewing machines to wind the thread for your embroidery projects. Never add thread to a partially wound bobbin, as it may be uneven and cause thread to tangle or break.