Dough Ruler Resopal - ThermohauserBack ruler Resopal, sturdy, white with black red scale, approx. 64. 5 cm x 5 cm he plastic baking rulers are ideal for measuring and dividing cake slices, etc. Each ruler has 3 useful divisions: The rulers are 64. 0 cm long, 5. 0 cm wide, and approximately 0. 2 cm thick. Two different plastic qualities are available, depending on your requirements: sturdy Resopal (natural white with a blue scale) or flexible polystyrene (PS, white with a red scale).