Tempera Blocks contain brilliant, opaque nontoxic tempera paint. Simply wet with water to use. For a bright, velvety texture, brush on any surface (even glass). When colors are mixed directly on the blocks, simply rinse with water for a fresh new surface of pure color. Each tempera block is 2-1/4" in diameter x 7/8" thick. One tempera block will cover more surface than a pint of liquid tempera paint. Holding tray is made of plastic.