Module 2,0 gears are used in combination with the module 2 racks we sell.
Most often a gearbox is needed in the system. Even with a small gear of 15 teeth the total distance travelled in one rotation is already 94.2mm. If a steppermotor or servo was directly attached this would result in a very fast system. Assuming a motor runs 1000 RPM, that would mean a feedrate of 94200mm/min. Most often we use a 1:10 gearbox so the max feedrate is reduced to 9420mm/min.
Take this into account when designing a machine with rack and pinion.