The 31.8mm standard is simply a larger diameter format for stems and handlebars. It is sometimes designated as "oversize", "OS", "NS" (New Standard), etc. For a long time, mountain bike handlebars used a 25.4mm (1") diameter at the clamp area. A slightly larger 31.8mm diameter provides greater stiffness with little additional weight. Since many road bikes use 31.8mm bars, stems can also be swapped between a wider range of bikes. By 2005 most manufacturers of bikes and components have switched to the 31.8mm standard for the majority of their high-performance products. Keep in mind that any bar and stem used together must be the same size, whether 26.0, 25.4 or 31.8.