Prevent thread tails from unwinding tangling with each other, and ensure neat storage and organization, they will make your sewing life easier. Works with the most preferred bobbin sizes (type L,class A and M ) These Clamps are made to last, High quality silicone that will hold bobbins tight to prevent unwinding Easy to use and ergonomically design Widely Used: These thread clamps work in most household sewing, embroidery spools, and ergonomically design, saving time to find small gaps in the spool to catch the thread.