A system for storing a first and a second substance (42a, 42b), the system comprising: - a container comprising a first compartment for storing a first substance and a second compartment for storing a second substance, for each compartment (41a, 41b) comprising: ∘ a plunger (10a, 10b) having a first end and an opposite second end, and comprising a passageway extending between the first and second ends, the plunger (10a, 10b) comprising at least one constriction arranged in the passageway between the first end and the second end; ∘ a plug (20a, 20b) being insertable into the passageway; ∘ wherein the diameter of the constriction is smaller than the smallest diameter of the plug (20a, 20b), at least in the area where the constriction seals with the plug (20a, 20b), ∘ wherein the constriction forms a sealing lip for forming a seal with the plug (20a, 20b); ∘ wherein the sealing lip is deformable by the plug (20a, 20b) pushed towards the first end of the plunger (10a, 10b), such that, once the plug (20a, 20b) is inserted into the passageway and reaches the sealing lip, the plug (20a, 20b) deflects the sealing lip and the sealing lip is biased against the plug (20a, 20b); - wherein the compartments (41a, 41b) store substances of a substantially incompressible material; characterized in that - the plugs (20a, 20b) are connected to each other by a connecting bar; - wherein the plungers (10a, 10b) are connected to each other at their second end by a connecting bar; - and wherein the plungers (10a, 10b) are advanceable to a position in which, due to different fill levels in the different compartments (41a, 41b), different amounts of excess substance have passed the constriction and are contained in the passageway of each plunger (10a, 10b), - wherein the plugs (20a, 20b) are insertable into the passageways until they reach and deflect the sealing lips to form a seal such that the excess substance contained in the passageway of each plunger (10a, 10b) is stored in the space between the plug (20a, 20b) and the plunger wall, and wherein - upon pushing the plugs (20a, 20b) further into the plungers (10a, 10b) the substantially incompressible material lifts the plungers (10a, 10b) until the connecting bar of the plunger (10a, 10b) contacts the connection bar of the plugs (20a, 20b). - a container comprising a first compartment for storing a first substance and a second compartment for storing a second substance, for each compartment (41a, 41b) comprising: ∘ a plunger (10a, 10b) having a first end and an opposite second end, and comprising a passageway extending between the first and second ends, the plunger (10a, 10b) comprising at least one constriction arranged in the passageway between the first end and the second end; ∘ a plug (20a, 20b) being insertable into the passageway; ∘ wherein the diameter of the constriction is smaller than the smallest diameter of the plug (20a, 20b), at least in the area where the constriction seals with the plug (20a, 20b), ∘ wherein the constriction forms a sealing lip for forming a seal with the plug (20a, 20b); ∘ wherein the sealing lip is deformable by the plug (20a, 20b) pushed towards the first end of the plunger (10a, 10b), such that, once the plug (20a, 20b) is inserted into the passageway and reaches the sealing lip, the plug (20a, 20b) deflects the sealing lip and the sealing lip is biased against the plug (20a, 20b); ∘ a plunger (10a, 10b) having a first end and an opposite second end, and comprising a passageway extending between the first and second ends, the plunger (10a, 10b) comprising at least one constriction arranged in the passageway between the first end and the second end; ∘ a plug (20a, 20b) being insertable into the passageway; ∘ wherein the diameter of the constriction is smaller than the smallest diameter of the plug (20a, 20b), at least in the area where the constriction seals with the plug (20a, 20b), ∘ wherein the constriction forms a sealing lip for forming a seal with the plug (20a, 20b); ∘ wherein the sealing lip is deformable by the plug (20a, 20b) pushed towards the first end of the plunger (10a, 10b), such that, once the plug (20a, 20b) is inserted into the passageway and reaches the sealing lip, the plug (20a, 20b) deflects the sealing lip and the sealing lip is biased against the plug (20a, 20b); - wherein the compartments (41a, 41b) store substances of a substantially incompressible material; - the plugs (20a, 20b) are connected to each other by a connecting bar; - wherein the plungers (10a, 10b) are connected to each other at their second end by a connecting bar; - and wherein the plungers (10a, 10b) are advanceable to a position in which, due to different fill levels in the different compartments (41a, 41b), different amounts of excess substance have passed the constriction and are contained in the passageway of each plunger (10a, 10b), - wherein the plugs (20a, 20b) are insertable into the passageways until they reach and deflect the sealing lips to form a seal such that the excess substance contained in the passageway of each plunger (10a, 10b) is stored in the space between the plug (20a, 20b) and the plunger wall, and wherein - upon pushing the plugs (20a, 20b) further into the plungers (10a, 10b) the substantially incompressible material lifts the plungers (10a, 10b) until the connecting bar of the plunger (10a, 10b) contacts the connection bar of the plugs (20a, 20b).