Threadless Stems 26.0mm
26.0mm is a road bike handlebar diamter standard but is fading from use as the larger 31.8mm standard becomes more common. It was used on most high quality road bikes from around 1985 until around 2008. Cheap road bikes will still often use a 25.4mm diameter, and older Cinelli bars and stems were the (now defunct) 26.4mm size.