Each bobbin is approximately 1.5 inches x 1.5 inches with the indent a bit narrower. Hope this helps!

And, each will hold 1 skein of floss very nicely. I would encourage you to use the plastic bobbins rather than the cardboard ones, if you decide to use them.

Plastic ones are much better. I cut the number of the color off the skein of floss and tape it on the bobbin, will fit between the slits. Also write it on other side with permanent marker so it will be on both sides.