Class 15 Confetti Cotton Thread Prewound Bobbins hold 100 yards (91 m) of 100% Egyptian cotton thread wound on a reusable plastic bobbin, which means there is no glue or wax holding it together (which also makes for happy machines). Prewound bobbins are a fantastic choice because they come wound uniformly, meaning you will get more consistency in all your stitches, which is especially noticeable when doing embroidery. They also come wound with a higher density of thread than when you wind your own bobbins on a domestic machine. 12 bobbins included per pack.