A shaft adapted to be at least partially inserted into an opening of a shaft receiver, said shaft having an axial extension along an axial direction and, in a direction along said axial direction towards an end of said shaft, said shaft comprises: - a nominal shaft portion adapted to be at least partially inserted into said opening of said shaft receiver, followed by - an intermediate shaft portion that in turn is followed by - a guide shaft portion terminating said shaft, said shaft having a central axis extending in said axial direction and being located in the centre of a cross-section perpendicular to said axial direction of said nominal shaft portion, said central axis extending in a direction from said nominal shaft portion towards said guide shaft portion, said shaft comprising a cross-section with a cross-sectional contour in a plane including said central axis, said cross-sectional contour comprising a nominal shaft portion contour of said nominal shaft portion, an intermediate shaft portion contour of said intermediate shaft portion and a guide shaft portion contour of said guide shaft portion, said cross-sectional contour comprising a radial direction being perpendicular to said central axis, wherein, in said radial direction, said nominal shaft portion contour is located at a nominal radial distance (R 0) from said central axis, characterized in that a smallest distance (R 1), in said radial direction, from said central axis to said intermediate shaft portion contour, occurs at an intermediate shaft portion contour trough and is less than 99%, preferably less than 95%, more preferred less than 90%, of said nominal radial distance (R 0), a largest distance (R 2), in said radial direction, from said central axis to said guide shaft portion contour, occurs at a guide shaft portion contour crest, is greater than said smallest distance (R 1), and is within the range of 95% to 100%, preferably within the range of 98% to 100%, of said nominal radial distance (R 0), said guide shaft portion contour comprising a guide shaft portion contour insert portion being located at a distance (C 1) of at least 1% of said nominal radial distance (R 0) in front of said guide shaft portion contour crest, in the direction of said central axis, wherein the distance (d 1), in said radial direction, from said guide shaft portion contour crest to said guide shaft portion contour insert portion is at least 1% of said nominal radial distance (R 0). - a nominal shaft portion adapted to be at least partially inserted into said opening of said shaft receiver, followed by - an intermediate shaft portion that in turn is followed by - a guide shaft portion terminating said shaft, said shaft having a central axis extending in said axial direction and being located in the centre of a cross-section perpendicular to said axial direction of said nominal shaft portion, said central axis extending in a direction from said nominal shaft portion towards said guide shaft portion, said shaft comprising a cross-section with a cross-sectional contour in a plane including said central axis, said cross-sectional contour comprising a nominal shaft portion contour of said nominal shaft portion, an intermediate shaft portion contour of said intermediate shaft portion and a guide shaft portion contour of said guide shaft portion, said cross-sectional contour comprising a radial direction being perpendicular to said central axis, wherein, in said radial direction, said nominal shaft portion contour is located at a nominal radial distance (R 0) from said central axis, characterized in that a smallest distance (R 1), in said radial direction, from said central axis to said intermediate shaft portion contour, occurs at an intermediate shaft portion contour trough and is less than 99%, preferably less than 95%, more preferred less than 90%, of said nominal radial distance (R 0), a largest distance (R 2), in said radial direction, from said central axis to said guide shaft portion contour, occurs at a guide shaft portion contour crest, is greater than said smallest distance (R 1), and is within the range of 95% to 100%, preferably within the range of 98% to 100%, of said nominal radial distance (R 0), said guide shaft portion contour comprising a guide shaft portion contour insert portion being located at a distance (C 1) of at least 1% of said nominal radial distance (R 0) in front of said guide shaft portion contour crest, in the direction of said central axis, wherein the distance (d 1), in said radial direction, from said guide shaft portion contour crest to said guide shaft portion contour insert portion is at least 1% of said nominal radial distance (R 0).