A device for preparing a bone cement paste consisting of two starting components, the device comprising a mixing unit comprising a hollow cylindrical cartridge that has an interior, wherein a bone cement powder is stored in the interior as a first starting component, and a cartridge head, which fluid-conductingly closes the interior at a proximal cartridge end, and the device comprising a reservoir for a monomer liquid as a second starting component, comprising a conduit means which fluid-conductingly connects the interior of the mixing unit to the reservoir, wherein the conduit means extends through a cartridge head duct of the cartridge head of the mixing unit, and the conduit means and the cartridge head duct form a first form-fitting connection, wherein the reservoir comprises a reservoir container, in which at least one fluid-conductingly closed ampoule, which has an ampoule body and an ampoule head, is arranged and the monomer liquid is stored in the ampoule, and comprises a cavity in the region of the ampoule head, wherein the cavity is fluid-conductingly connected to the conduit means and comprises a connection to the ampoule, wherein the ampoule head is arranged with at least some regions in the connection and the reservoir container comprises, at least in some portions, a deformable region, so that the ampoule can be tilted about a pivot point against the connection, wherein the connection has a connection diameter which is adapted to the dimensions of the ampoule head in such a way that the ampoule head can be fluid-conductingly opened when the ampoule is tilted about the pivot point against the connection, and wherein the reservoir has a connecting element for connecting the reservoir to the mixing unit via a second form-fitting connection. a mixing unit comprising a hollow cylindrical cartridge that has an interior, wherein a bone cement powder is stored in the interior as a first starting component, and a cartridge head, which fluid-conductingly closes the interior at a proximal cartridge end, and the device comprising a reservoir for a monomer liquid as a second starting component, comprising a conduit means which fluid-conductingly connects the interior of the mixing unit to the reservoir, wherein the conduit means extends through a cartridge head duct of the cartridge head of the mixing unit, and the conduit means and the cartridge head duct form a first form-fitting connection, wherein the reservoir comprises a reservoir container, in which at least one fluid-conductingly closed ampoule, which has an ampoule body and an ampoule head, is arranged and the monomer liquid is stored in the ampoule, and comprises a cavity in the region of the ampoule head, wherein the cavity is fluid-conductingly connected to the conduit means and comprises a connection to the ampoule, wherein the ampoule head is arranged with at least some regions in the connection and the reservoir container comprises, at least in some portions, a deformable region, so that the ampoule can be tilted about a pivot point against the connection, wherein the connection has a connection diameter which is adapted to the dimensions of the ampoule head in such a way that the ampoule head can be fluid-conductingly opened when the ampoule is tilted about the pivot point against the connection, and wherein the reservoir has a connecting element for connecting the reservoir to the mixing unit via a second form-fitting connection.