A casing for coaxially receiving and fitting a cartridge or a cartridge-like container on an ejection device for ejecting a viscous compound, wherein at least one shell portion of the casing is telescopic, and wherein the telescopic portion has at least two tubular portions which are arranged coaxially to one another in certain portions, and which are displaceable relative to one another in the axial direction. The tubular portions are inter-engaged via latching elements and can be locked relative to one another in different positions, and that the first tubular portion has a flange with a coupling element at a first end and can be releasably connected by the coupling element to the ejection device directly or via an intermediate piece, and that the first tubular portion has a sliding portion on which the second tubular portion is displaceable between a first locked position into a second locked position.