Abstract: A device for mixing two components, at least one of them a liquid, has a barrel with a wide-open end receiving a tubular plunger having an extremity open toward the barrel. The plunger is provided at that extremity with a relatively rotatable plug, fitting slidably into the open barrel end, and forms an outlet for the contents of that plunger which can be opened or closed by such relative rotation whereby the plug/plunger assembly can be filled with one component and sealed before being introduced from above into the barrel loaded with the other component. Either the plug or the plunger consists of elastic material and the plunger or the barrel may be provided with a sealable discharge opening which can be fitted with a needle when the device is to be used as a syringe.