The thomson elite x4 stem grew out of the legacy of the thomson elite line a great all around modern stem to fit 318mm diameter handlebars this stem is ready to ride where you are the design team for the new thomson x4 had a tough goal make a stem better than the thomson elite 254 early tests showed us that our competitors 318 stems were heavier and weaker than our thomson elite 254 at thomson the x4 was not done until it was stronger lighter and longer lived than the legendary thoms