A stance phase flexion device for a prosthesis comprises a composite C-shaped spring member formed from a plurality of thermoset synthetic resin-impregnated high strength carbon filament sheets molded together in a compression mold. The spring member includes a standard hole pattern located in an upper leg of the spring and a standard hole pattern on the lower leg of the spring, for connecting the spring between adjacent prosthetic components for simulating normal flexion between the adjacent components. The C-shaped member is normally rigid in a rest position maintaining its C-shaped configuration. The C-shaped member has spaced apart upper and lower legs that elastically flex with energy absorbing compliance under a load tending to move the upper and lower legs together. The C-shaped member essentially resists elastic flexion in lateral directions and resists torsion loads.