Convenient for plastic or metal bobbins. Accepts 1” diameter Class M bobbins. Bobbin threads won’t table or unwind. Holds over 20 bobbins! If bobbins are too loose, you can reshape the bobbin channel. Submerge BobbinSaver® in boiling water for 15 - 20 seconds. Remove and press sides together evenly around the circle. Dip in cold water to set.