Robot arm with - an axial unit which comprises an axial guide and is fastened to the robot arm, - an axial strut which is movable relative to the axial guide in its axial direction, - the guide surfaces of the axial guide guide the axial strut in a rotationally fixed manner - in that the axial guide, viewed in the axial direction, has a non-circular inner contour which interacts positively with a correspondingly non-circular outer circumference of the axial strut, - the axial strut, viewed in the axial direction, has at least three guide surfaces (30.1 - 30.3) which run in the axial direction and against each of which at least one guide body of the axial guide bears, - in the case of at least one of the guide surfaces (30.1), the at least one guide body resting thereon is prestressed in the direction of this guide surface (30.1) by means of a prestressing device or vice versa, - wherein two guide bodies (31a, b) are arranged spaced apart in the axial direction and bear against the same guide surface (30.1), - the pre-tensioning of the guide bodies (31a, b) - either with respect to the basic body of the axial guide by means of springs - or with respect to one another by means of a tension spring in such a way that the pretensioning device present for each guide body has a component which points in the direction of the axial strut, i.e. the centre of the cross-section of the axial guide, and has a component which is conditioned by the pretensioning of the two guide bodies (31a, b) with respect to one another and points towards the other guide body, characterIsed In that - the tension spring is received in a spring recess open towards the outer circumference of the base body of the axial guide in such a way that the tension spring can be gripped and replaced from the outer circumference. - an axial unit which comprises an axial guide and is fastened to the robot arm, - an axial strut which is movable relative to the axial guide in its axial direction, - the guide surfaces of the axial guide guide the axial strut in a rotationally fixed manner - in that the axial guide, viewed in the axial direction, has a non-circular inner contour which interacts positively with a correspondingly non-circular outer circumference of the axial strut, - the axial strut, viewed in the axial direction, has at least three guide surfaces (30.1 - 30.3) which run in the axial direction and against each of which at least one guide body of the axial guide bears, - in the case of at least one of the guide surfaces (30.1), the at least one guide body resting thereon is prestressed in the direction of this guide surface (30.1) by means of a prestressing device or vice versa, - wherein two guide bodies (31a, b) are arranged spaced apart in the axial direction and bear against the same guide surface (30.1), - the pre-tensioning of the guide bodies (31a, b) - either with respect to the basic body of the axial guide by means of springs - or with respect to one another by means of a tension spring in such a way that the pretensioning device present for each guide body has a component which points in the direction of the axial strut, i.e. the centre of the cross-section of the axial guide, and has a component which is conditioned by the pretensioning of the two guide bodies (31a, b) with respect to one another and points towards the other guide body, - either with respect to the basic body of the axial guide by means of springs - or with respect to one another by means of a tension spring in such a way that the pretensioning device present for each guide body has a component which points in the direction of the axial strut, i.e. the centre of the cross-section of the axial guide, and has a component which is conditioned by the pretensioning of the two guide bodies (31a, b) with respect to one another and points towards the other guide body, - the tension spring is received in a spring recess open towards the outer circumference of the base body of the axial guide in such a way that the tension spring can be gripped and replaced from the outer circumference.