The invention relates to a needle-less, disposable injector comprising a housing (10), which has at least one compression bar, a cylinder-piston unit (100), a plunger-actuating ram (60), a trigger unit (80) and a spring energy reservoir (50), wherein the trigger unit locks the pretensioned spring energy reservoir by means of the compression bar. During triggering, the compression bar slides along at least one trigger element (82) of the trigger unit and, after triggering the trigger unit, the spring energy reservoir displaces the compression bar by means of the plunger-actuating ram and actuates the cylinder-piston unit. When loaded by the pretensioned spring energy reservoir, the pairing formed by the mutually facing inner wall of the trigger element and the contact surface of the compression bar has at least in areas a higher sliding friction coefficient than the pairing formed by the mutually facing collar surface of the plunger-actuating ram and the support surface of the compression bar. The present invention provides a disposable injector where the required minimum contact-pressure force is ensured during use thereof.