Naturally these wonderfully sized bobbins fit the Woolee Ann and hold about 8 oz. of yard compared to our 4 oz bobbins. With the easy change bobbin system and their great capacity= more spinning time vs less fuss changing time. I would suggest getting at least a couple extra bobbins at time of purchase, if you do much spinning at all. (Having to leave newly spun yarn sitting over night to set the twist can quickly use up 3 bobbins.) Happy spinning!