BobbinSaver holds any and all bobbins - small or large, metal or plastic - and their threads won't tangle or unwind. It is made of a flexable rubbery type plastic that will hold any size bobbin. It will even stay in place even if the ring is turned upside down, yet it is very easy to remove a bobbin by hand. Will hold around 20 large bobbins or 30 small bobbins. 1/pkg.