shown at 71 a in fig3 frustoconical is intended to mean shaped like the frustum of a cone that is it has the shape of the basal part of a solid cone formed by cutting off the top by a plane parallel to the base the smallest illustrated diaphyseal implant component 52 a also has a first annular step 72 a and a last annular step 74 a in each of the other sizes of diaphyseal implant components 52 b 52 c 52 d 52 e in the set 50 the tapered outer surface 60 b 60 c 60 d 60 e comprises a plurality of annular steps there is a first step 72 b 72 c 72 d 72 e between the first end 54 b 54 c 54 d 54 e and second end 56 b 56 c 56 d 56 e of the diaphyseal implant components a last annular step 74 a 74 c 74 d 74 e at the second end 56 b 56 c 56 d 56 e of the diaphyseal implant component and a plurality of intermediate steps 76 b 76 c 76 d 76 e between the first step 72 b 72 c 72 d 72 e and last step 74 a 74 c 74 d 74 e each step has a substantially cylindrically shaped outer surface and a longitudinal height the largest diameter steps deviate from a cylindrical shape in the illustrated embodiments because of the presence of the four flats.