Originally Posted by HillRider
It seems a lot of bar/stem manufacturers try to make their sizes sound proprietary hoping customers will feel compelled to buy both from them. The 25.8 and 25.9 mm advertised bars/stems sizes in places of the "standard" 26.0 mm was a similar situation.
Actually no. 25.8 and 26.0 is different.
You can force these different parts to work together since the difference is small but if you compare the fit carefully, there is a definite difference - hold a open faced 25.8mm stem up against some 26.0mm bars and the bars will not seat down into the stem evenly.
31.7 and 31.8 ARE the same since the true size is 1-1/4" (31.75mm)