Glass seed beads are small, usually round beads of near uniform size. They are used for stringing, jewelry, embellishments for clothing and accessories, loom weaving, and more.
Glass seed beads come in a variety of styles, finishes, colors, and sizes. They are sized by number, referred to as "aught" which is often seen written as something like "10/0" and spoken as "ten-aught". Generally the higher the number the smaller bead, so for example a 10/0 glass seed bead would be smaller than a 3/0 bead.
While the aught system of classifying glass seed beads is widely used it is not absolute and will vary somewhat between manufacturers and countries of origin. Below is a chart to give a general reference of aught sizes.