The invention relates to an attachment (10) for a standard injection device (70) for needleless injection of a fluid, having a nozzle adapter (12) and a piston unit (40), wherein the nozzle adapter (12) comprises a skin contact surface (16) arranged on the distal end (14) thereof having an outlet opening (18), a first cylinder section (20) connecting proximally to the outlet opening (18) and a second cylinder section (26) connecting to the first cylinder section (20), and the piston unit (40) is mounted in a movable manner in the first cylinder section (20) to form a piston-cylinder unit and the attachment (10) has a fluid line (48) for transporting fluid from the standard injection device (70) to the outlet opening (18).
