A dispenser for dispensing flowable masses has a reservoir and a modular dispenser pump with an input channel, an output channel and a pump chamber. A head piece is provided and has a dispensing opening and a dispensing channel. The dispenser pump can be inserted into the reservoir and can be connected to the reservoir by a locking connection. The pump chamber is formed by a piston and a cup part. The piston is slidably accommodated in the cup part. The cup part has fastening formations for fastening interaction with an inner wall of the reservoir. The locking connection is provided by two radially outwardly protruding locking beads, which are spaced apart from one another in the vertical direction. The locking beads are designed with an insertion rounding on the reservoir side and with a substantially horizontal contact surface with respect to the longitudinal section on the head piece side.