You don't know what you've got 'till it's gone . . . .
or until you've run out.
How true that is! That's how I felt when I needed to grab a project in progress so I could work on it at the shop. I needed to wind my thread around a plastic bobbin to keep it from tangling and I couldn't find any. Or more accurately, I couldn't find any that were not already in use.
Sure, I can improvise. I can wrap the thread around a piece of cardboard and all will be fine. But you know how you start using a convenience and it becomes, oh, convenient? I didn't quite realize how much I used these nifty little items until I didn't have one ready to use.
The bobbins are available in different sizes -- we carry the 1 7/8 inch size (the most commonly used size) and the larger 2 1/2 inch size. The larger size is great if you're using thicker cords or beads in your project. If these are not already a standard item among your supplies you might want to consider adding them.