Stamps4Clay Stm stamps from MKM Pottery Tools help you create beautiful and unusual patterns and textures in the clay pieces you throw and create. Stm stamps measure approximately 3cm x 3cm. All MKM stamps are carved at the MKM factory by MKM employees. That means quality in the original wood blank material, quality of design, and quality of carving, quality of wood finish (teng oil), and, of course, quality service to all of our customers.