I meant that it becomes critical from a height of 2 cm. But you have to set a guide and limit cable. This ensures that the robot stops in time and does not drive over predefined edges. This is all wonderfully described in the instruction manual (https://www.gardena.com/ch-de...). Another personal tip: if in doubt, take the larger model. In my case, the 250 model has trouble reaching all the spots (even though I only have 200m2 of lawn).