A quick-connect coupling for connecting an exchangeable head to a pressing device, wherein a number of balls with a diameter is radially movably disposed in a single ball-holding part on the pressing device and wherein a peripheral groove with a groove depth to partially hold the balls is present on a shaft part with a radius with the pressing device and the exchangeable head in a connected state and wherein a single locking ring is movably attached to the ball-holding part in an axial direction, the balls being held radially fixed in the peripheral groove by said locking ring when the pressing device and the exchangeable head are in the connected state, and where furthermore - on the shaft section of the exchangeable head there is a further peripheral groove, which is disposed closer to the pressing device in an axial direction, namely at a distance (d) from the peripheral groove, and the further peripheral groove is designed to hold further balls, also with the diameter, wherein the further balls are likewise disposed in a radially movable manner in the ball-holding part and wherein the balls and the further balls in the ball-holding part are likewise spaced at a distance (d), wherein in the ball-holding part, balls and further balls are disposed in ball guides (5, 6) such that they are radially movable and balls (K1, K2) and the ball guides (5, 6) are distributed over the periphery of ball-holding part, and the locking ring has locating grooves (7, 8) on the inside, which are formed so that the balls (K1, K2) can move away into the locating grooves (7, 8) when the locking ring is in the unlocked position, characterised in that - the shaft part is disposed in an area that is closer to the pressing device in an axial direction and is likewise spaced at distance (d) from the further peripheral groove, exhibits a form executed as an extension of the shaft part end with a constant radius at least at distance d from the peripheral groove, preventing the further balls from moving radially when contact is made with the further balls and therefore preventing the locking ring from moving, such that it is impossible to lock the exchangeable head in the wrong position. - on the shaft section of the exchangeable head there is a further peripheral groove, which is disposed closer to the pressing device in an axial direction, namely at a distance (d) from the peripheral groove, and the further peripheral groove is designed to hold further balls, also with the diameter, wherein the further balls are likewise disposed in a radially movable manner in the ball-holding part and wherein the balls and the further balls in the ball-holding part are likewise spaced at a distance (d), wherein in the ball-holding part, balls and further balls are disposed in ball guides (5, 6) such that they are radially movable and balls (K1, K2) and the ball guides (5, 6) are distributed over the periphery of ball-holding part, and the locking ring has locating grooves (7, 8) on the inside, which are formed so that the balls (K1, K2) can move away into the locating grooves (7, 8) when the locking ring is in the unlocked position, characterised in that - the shaft part is disposed in an area that is closer to the pressing device in an axial direction and is likewise spaced at distance (d) from the further peripheral groove, exhibits a form executed as an extension of the shaft part end with a constant radius at least at distance d from the peripheral groove, preventing the further balls from moving radially when contact is made with the further balls and therefore preventing the locking ring from moving, such that it is impossible to lock the exchangeable head in the wrong position.