A planetary gear reduction starter has packing designed to absorb the variations in the axial dimension of a component, so that it eliminates the need of tight control of the axial dimension of the component and enables lower cost, higher productivity, and reduced size of the completed starter. The packing is constituted by an annular section, a jaw which extends in the radial, inward direction from one end of the annular section, and a plurality of projections which are laid out radially at equiangular pitches on the inner surface of the jaw and which have a semicircular section. The annular section of the packing is fitted around the outer peripheral surface of an internal gear assembly and the jaw is held in a compressed state between the end surface of the internal gear assembly and the side surface of the plate. The compressive deformation of the projections varies according to the axial dimension of the internal gear assembly or the plate, thereby absorbing the variations in the axial dimension.