Abstract: A seat reclining mechanism including a cushion arm pivotally connected to a squab arm by a planetary gear arrangement, the planetary gear arrangement including a pair of side by side ring gears, one of the ring gears being secured to the squab arm and the other of the ring gears being secured to the cushion arm, a sun and planetary gear arrangement common to both ring gears, the sun and planetary gear arrangement including a plurality of radially movable planetary gears surrounding a sun gear assembly, the sun gear assembly including at least one axially movable frusto-conical sun gear in engagement with said planetary gears, the at least one frusto-conical sun gear being axially biased so as to bias sun gear member into full meshing contact with the planetary gears and thereby bias the planetary gears in a radially outwards direction to a radially outermost position whereat the planetary gears are in full meshing contact with said ring gears, the sun gear assembly including a stop sun gear axially juxtaposed