Shaped like half of a bagel and hollowed out, it is made of flexible rubbery plastic 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.