Metering device (1,11,111) for metered output of a liquid preparation comprising at least a first and a second starting substance, the metering device (1,11,111) having a storage vessel, for receiving at least the first starting substance, with at least one opening, and an output unit having at least one passage channel with two channel openings, the output unit (4,40) and the storage vessel being disposed relative to each other such that one of the channel openings and the opening of the storage vessel are orientated towards each other and the output unit (4,40), in the region of the opening of the storage vessel, is connected to the storage vessel in a sealed manner, the region of the output unit (4,40) orientated towards the storage vessel being configured as a penetration unit which can be introduced into the opening of the storage vessel and/or can be guided in the latter; and in the region of the opening of the storage vessel between storage vessel and output unit (4,40), an inner vessel, which is sealed at least relative to the storage vessel, for receiving the second starting substance being disposed, the inner vessel being able to be penetrated with the help of the penetration unit of the output unit (4,40), characterised in that the output unit (4,40) has a hollow cylinder or a hollow prism which surround the penetration unit; in that the hollow cylinder or the hollow prism have undercuts on their inside at least in regions; in that the storage vessel has undercuts in the region of its opening, the undercuts of the hollow cylinder or of the hollow prism and those of the storage vessel preferably being in direct or indirect engagement after penetration of the inner vessel; and in that the output unit (4,40) and the opening of the storage vessel are connected by means of a flexible plastic material tube, the plastic material tube having at least respectively at least one thickened portion preferably in the regions which are connected to the hollow cylinder or hollow prism and/or to the storage vessel, which thickened portion is in engagement with the undercuts on the inside of the hollow cylinder or of the hollow prism and/or with the undercuts in the region of the opening of the storage vessel. the output unit (4,40) has a hollow cylinder or a hollow prism which surround the penetration unit; in that the hollow cylinder or the hollow prism have undercuts on their inside at least in regions; in that the storage vessel has undercuts in the region of its opening, the undercuts of the hollow cylinder or of the hollow prism and those of the storage vessel preferably being in direct or indirect engagement after penetration of the inner vessel; and in that the output unit (4,40) and the opening of the storage vessel are connected by means of a flexible plastic material tube, the plastic material tube having at least respectively at least one thickened portion preferably in the regions which are connected to the hollow cylinder or hollow prism and/or to the storage vessel, which thickened portion is in engagement with the undercuts on the inside of the hollow cylinder or of the hollow prism and/or with the undercuts in the region of the opening of the storage vessel.