There are four sizes: Small(12mm x 15 mm), Medium(15mm x 17 mm) , Large (17mm x 20 mm), and Extra Large (20mm x 22 mm).
Bisqued beads are great to buy even if you don't have a kiln. Acrylic paints and stains look great on a bisqued bead -- and to make them even shiner add a coat of gloss sealer. There are also paints specifically made for bisqued ceramics. Your local ceramics shop can show you around or you can search for the term "ceramics" and order online. I've even glazed bisqued beads with nail polish and even after several years have seen no signs of aging, chipping, or turning "yellow". Art Clay Silver artists cover bisqued beads with Fine Silver with beautiful results.