Abstract: An apparatus for the dimensionally accurate cutting of a product carrier (1) which is in the form of a strip, is transported further in a cyclic or continuous manner in the longitudinal direction and has cells which are arranged one behind the other and are sealed in an airtight manner comprises a rotating cutter roller (15), which severs the product carrier (1) in each case in the region of a sealing web (4) which is situated between two cells (2), is arranged transversely with respect to the longitudinal direction and is provided with a lattice-like embossing (19). In order to identify and localise the sealing web (4), an optical reflection sensor (6) is arranged above and/or below the product carrier (1) and generates an AC voltage signal which corresponds to the lattice structure when the sealing web (4) is located in the region of the reflection sensor (6), the number of periods being a measure of the width b of the sealing web (4).