The X4 is absolutely the best combination of strength and weight available. Enduro and downhill riders can run Thomson confidently. X4 offers precise steering and tracking for the ultimate in control while riding. 32mm, 40mm, and 50mm stems are available in block style only. The Thomson 35mm X4 stem allows you to realize the benefits of stiffer forks and stiffer 35mm bars. X4 offers precise steering, tracking, and more control while riding, all wrapped up in a beautiful design.