For continuous, uniform material processing in the field of sealing technology, the gap between the rolls must be set with the hydraulic adjustment device and maintained constant. For this reason the top and bottom rolls are provided with a shoulder and an aluminum ring as measurement objects to the left and right. Using the aluminum ring, errors due to the roll material can be avoided. Two eddy current sensors mounted opposite one another measure the distance to the aluminum ring from a fixed reference point. The roll gap can be found from the sum of the two distances.