A abstract an angular reducer with two or three reduction stages wherein the casing is designed to selectively house two or three reduction stages while maintaining unchanged when switching from two to three stages or vice versa the mutual positions of the axis of the drive shaft and the axis of the driven shaft and wherein the casing has a number of inner supports for supporting the two alternative gear trains application_number US 81250097 A description in the fig1 and 2 embodiment the angular reducer 1 comprises two reduction stages 3 4 housed inside a casing 2 the first stage 3 comprises a first cylindrical gear 32 of axis k integral with a drive shaft 31 and which meshes with a second cylindrical gear 5 fitted to a shaft 6 supported by two bearings 7 8 the second stage 4 in the fig1 and 2 embodiment comprises a hypoid bevel pinion 9 meshing with a bevel ring gear 10 integral with a driven shaft 11 of axis m fig2 as shown in fig1 and 2 the hypoid pinion 9 is supported by the same shaft 6 to which the second cylindrical gear 5 is fitted and which as stated is in turn supported by the bearings 7 8 which are supported by inner supports 12 13 the casing 2 comprises a number of walls 14 19 defining a box structure wall 14 comprises an opening 20 through which motion is transmitted from the first cylindrical gear 32 to the second cylindrical gear 5 and seats 21 22 fig2 are formed respectively in walls 18 19 to support the driven shaft 11 by means of bearings 24 25 and therefore also support the bevel ring gear 10 integral with the driven shaft 11 in.