Beads are categorised by material, shape, colour and size. Bead sizes range from very small 24° ("24-aught" or 24/0) about the size of a grain of sand, to big 1°. The unit of bead size was traditionally defined as the number of seed beads that fitted into an inch length, hence the reason why the smaller beads are defined by a bigger number than the larger beads. Whenever you create beaded jewellery always check the uniformity of the beads you are going to use. When you sew peyote stitch etc, odd sized, odd shaped and broken beads can warp your work out of shape and make it look not as pleasing to the eye.