Vortex Bright Green/black Countup&down d20 Single Die (1 piece) (Chessex) (XVUD00)Our Countup&down dice are a unique tool for games that require keeping a counter. If you position the dice on the table so that the number is facing upward, the next number down will always be the number below. For ease of use, on each face there is an indicator pointing towards the next highest number. They are larger than our normal 18mm d20s. These are 25mm in diameter from face to face. Vortex is a registered trademark of Chessex Manufacturing.