There are two measures of custom grips, the valid grips for handlebars of 22mm and the valid ones for handlebars of 25.4mm or 1" which is the same, you only have to measure the diameter of your handlebar where the grips are installed and you can already choose between the wide range of custom motorbike grips which you like to customize your custom motorcycle.You will also have to take into account if you need some fists without a rod or with a rod, if they are with a rod you should make sure they are valid for your  custom motorbike model and year.