An attachment part (10") for tightening joints, comprising: - an elongate housing (11,12) including an upper housing part and an interconnected lower housing part, - an input gear wheel for connection to an output shaft of a power wrench, which input gear wheel is arranged at a first end of the housing, - an output gear wheel for connection to a joint to be tightened, which output gear wheel is arranged at a second end of the housing, and - at least one intermediate gear wheel (24,25,26), which is arranged inside the housing (11,12) to transmit the rotation of the input gear wheel to the output gear wheel, wherein each gear wheel has outer slanted teeth that connect the gear wheels and transmit said rotation there between, whereby the at least one intermediate gear wheel (24,25,26) comprises: - an upper race, which is arranged inside the at least one intermediate gear wheel (24,25,26) and faces the upper housing part, wherein balls are arranged in said upper race at least partly inside the at least one intermediate gear wheel (24,25,26) to support an upper part of it with respect to the housing (11,12), and - a lower race, which is arranged inside the at least one intermediate gear wheel (24,25,26) and faces the lower housing part, wherein balls are arranged in said lower race at least partly inside the at least one intermediate gear wheel (24,25,26) to support a lower part of it with respect to the housing (11,12), characterised in that the balls (28,38) in the upper and lower races (27,52) are fully supported by upper and lower axial supports (29',30',31'; 32',33',34'), respectively, which axial supports (29',30',31'; 32',33',34') are connected to each other via an attachment piece that runs through the centre of the intermediate gear wheel (24,25,26), such that an upper and lower axial support (29',30',31'; 32',33',34'), balls (28,38), and a gear wheel forms a releasable gear package. - an elongate housing (11,12) including an upper housing part and an interconnected lower housing part, - an input gear wheel for connection to an output shaft of a power wrench, which input gear wheel is arranged at a first end of the housing, - an output gear wheel for connection to a joint to be tightened, which output gear wheel is arranged at a second end of the housing, and - at least one intermediate gear wheel (24,25,26), which is arranged inside the housing (11,12) to transmit the rotation of the input gear wheel to the output gear wheel, wherein each gear wheel has outer slanted teeth that connect the gear wheels and transmit said rotation there between, whereby the at - an upper race, which is arranged inside the at least one intermediate gear wheel (24,25,26) and faces the upper housing part, wherein balls are arranged in said upper race at least partly inside the at least one intermediate gear wheel (24,25,26) to support an upper part of it with respect to the housing (11,12), and - a lower race, which is arranged inside the at least one intermediate gear wheel (24,25,26) and faces the lower housing part, wherein balls are arranged in said lower race at least partly inside the at least one intermediate gear wheel (24,25,26) to support a lower part of it with respect to the housing (11,12),