here is a shot of the bolt pattern, it is 1mm holes with a 6.35mm spacing with 3mm center hole. this is the same as the pololu hubs and many more
this is a wheel for a robot or rc car or whatever it has a 3mm hole in the middle that can be drilled out for larger gear motors. it has a standard mounting pattern that most companies use.
3.768 w x
5.5 d x
1.483 w x
2.165 d x