An insert (10, 12, 13, 14, 15) for an opening on a tube of a bicycle frame, wherein the opening is arranged on the lateral area of the tube, comprising - at least one through hole (27, 28, 87) for passing a wire, a cable or a hydraulic line through the opening and into the tube or out of the tube, - a first insert element (21, 81, 151, 161) which, in the mounted position, is arranged essentially outside the tube, - a second insert element (22, 82) which, in the mounted position, is arranged essentially inside the tube and the side walls of which are formed such that they can be pushed into the opening at least in part, - a fixing means for fixing the first and second insert elements to each other, wherein - the first and second insert elements are connected to each other via the fixing means such that they can be held relative to each other in a first position and in a second position, wherein the first position determines a mounting position for mounting the second insert element in the opening and the second position defines a holding position of the two insert elements relative to each other in which, in the mounted position, the first and second insert elements clamp a section of the side wall of the tube, more particularly a section adjacent to the opening, from the inside and from the outside, whereby the insert is held in the opening, characterised in that at least the second insert element (22, 82) which, in the mounted position, is arranged essentially inside the tube and the side walls of which are formed such that they can be pushed into the opening at least in part essentially remains free from deformations in the second position, i.e., in the holding position, in which the two insert elements are located relative to each other, in comparison to the first position, i.e., the mounting position, wherein the change in shape of the second insert element in a specific direction of a Cartesian coordinate system with X-, Y-, and Z-axes, in which the respective insert element is arranged, remains less than 10 % of the maximum dimensions, in this direction, of the insert element in each direction of this coordinate system. - at least one through hole (27, 28, 87) for passing a wire, a cable or a hydraulic line through the opening and into the tube or out of the tube, - a first insert element (21, 81, 151, 161) which, in the mounted position, is arranged essentially outside the tube, - a second insert element (22, 82) which, in the mounted position, is arranged essentially inside the tube and the side walls of which are formed such that they can be pushed into the opening at least in part, - a fixing means for fixing the first and second insert elements to each other, wherein - the first and second insert elements are connected to each other via the fixing means such that they can be held relative to each other in a first position and in a second position, wherein the first position determines a mounting position for mounting the second insert element in the opening and the second position defines a holding position of the two insert elements relative to each other in which, in the mounted position, the first and second insert elements clamp a section of the side wall of the tube, more particularly a section adjacent to the opening, from the inside and from the outside, whereby the insert is held in the opening, characterised in that at least the second insert element (22, 82) which, in the mounted position, is arranged essentially inside the tube and the side walls of which are formed such that they can be pushed into the opening at least in part essentially remains free from deformations in the second position, i.e., in the holding position, in which the two insert elements are located relative to each other, in comparison to the first position, i.e., the mounting position, wherein the change in shape of the second insert element in a specific direction of a Cartesian coordinate system with X-, Y-, and Z-axes, in which the respective insert element is arranged, remains less than 10 % of the maximum dimensions, in this direction, of the insert element in each direction of this coordinate system.