These porcelain mugs are ideal for coffee or tea. They are hand-thrown and fired with a unique crystal glaze. These glazes are notoriously difficult to perfect. They form in the same way as ice crystals, but instead of forming at freezing temperatures, they form at 2,000 degrees Fahrenheit. The nature of crystal glazes is variation, so each mug has a different pattern of crystals. Also, being hand-made, the mugs vary in size. I strongly suggest that you visit me in my studio to choose the mug you like the most. This also avoids the hassle and expense of shipping.