The design team for the new Thomson 31.8 stems had a tough goal: make a stem better than the Thomson Elite Road and Mountain Stems. Early tests showed us that Thomson competitors 31.8 stems were heavier and weaker than Thomson Elite 25.4 and 26.0 stems.The Thomson X4 for Mountain and X2 for Road allow you to realize the benefits of stiffer forks and stiffer 31.8 bars. They offer precise steering, tracking, and more control while riding, all wrapped up in a beautiful design.The Thomson X4 is stronger and 30 grams lighter than the Thomson Elite 25.4 mountain stem. It features a traditional steerer clamp that is shaped to save weight and to be knee friendly. Light enough for Cross Country or Road is only part of the storyThe X4 is absolutely the best combination of strength and weight available. Thomson stems are the strongest in the industry, meaning freeride and downhill riders can run Thomson confidentlySM-E155B - for 1.5 inch headset.