250mm x 12mm, Large size, measure up to 240mm (9 1/2 inches) wide and 230mm (9 inches) deep.
2 in 1, (bottom thickness and Tombo) Stainless Steel Pottery Measuring Tools by Master Potter Hsin-Chuen Lin
1. Get exact measurement of the bottom thickness before trimming, and while trimming, constantly check how much clay can be removed so that it won't be cut through or left too thick.
2. A clever update of the classic “Tombo” sticks. By adding o-rings to the rulers, people can hold the tools in positions to get more accurate measurement when making sets of cups/bowls.