Generally, the size of the servo flange used more is as follows, 40*40, 60*60, 80*80, 90*90, 110*110, 130*130, 150*150, 180*180 and some larger sizes are not listed here.
There are two situations that need to be paid attention to when using servo motors to match reducers, one is that they have servo motors, and the other is that they have suppliers who match motor reducers. In the former case, it is necessary to provide the size of the flange, and it is clear what the size of the various sizes is. In the latter case, there is no need to provide the relevant size, because the merchant can directly connect the reducer and the servo motor to match, so there is no need to consider the size of the various sizes.
If you belong to the former, you need to carefully check the various sizes, so as not to have the problem of different screw hole sizes or different interfaces, resulting in installation and return and replacement.