A convertible has a top which can be opened and can be put away and which has a rear window frame and, when the top is closed, at least one surface bow situated in front of said rear window frame in the direction of travel. An essentially cylindrical pipette shaft with an internal diameter and an essentially cylindrical cup-shaped pipette reservoir with an internal diameter are produced in an injection molding process. Chip occupying area of the group of wirings and the buffer circuit is reduced.