The S2 31.8 bar is our lightweight, alloy mountain bike bar with a 31.8mm clamp diameter. Designed with the toughest riders in mind and a shape optimised for comfort and control, these bars will keep your wrists happy. The S2Â 31.8 bar features a new finish to help hold the stem and grip in position with easy cut markings and a custom swaging process for an optimal strength to weight ratio.