The BobbinSaver holds metal or plastic bobbins of all different sizes! Shaped like half of a bagel and hollowed out, it is made of flexible silicone that expands to receive the bobbin and promptly snugs up around it. Threads won't tangle or unwind. BobbinSaver holds over 20 bobbins securely. BobbinSaver is a simple elegant gadget to store any kind of bobbin. Unit measures 3/4" tall and 5 1/8" diameter.