I used the tip for buying the clear plastic 1/2 inch diameter hose for my bobbins. You cut a 1/4 section off the hose and cut a slit down one side to open it. You then push the little ring onto the bobbin to keep the thread contained. It also works great for identifying the thread that's on the bobbin. I write with a sharpie on the tube piece what the name of the thread is but you could write which machine the bobbin belongs to also.