I instead use soda/water plastic bottles to control the thread of the spool. Works like a charm! Learned that couple years ago when I started going to a Tuesday night sew group in town.
Here is a photo of what I'm talking about. I have also used the smaller water/soda bottle for regular sized spool threads.
I simply cut the bottle across at one of the seams usually about 1/4 or 1/3 up, put the spool of thread in than put the top piece on and overlap it with bottom piece and there you have it. When not in use I put the cap back on to keep it dust free.
