The thomson elite x4 15 stem thomson x4 one point five stems feature custom heat treated bolts with corrosion preventative plating thomson elite x4 15 stem features machined 7000 series extruded bar stock with new steerer clamp assembly custom heat treated bolts with corrosion preventative plating 318mm bar clamp with smooth edges for carbon bars 15 steerer 41mm height stem length 45mm stem angle 0 deg bar clamp diameter 318mm steerer tube 1