I just got in the 5" robot chassis with motors/wheels/etc. Unfortunately the ball caster I ordered doesn’t fit the chassis. I’ve been looking at the specs for some others, but it looks like they just don’t fit the holes in the chassis. Could you point me at a ball caster that will fit this?
The ball casters that work with the Pololu 5" Robot Chassis RRC04A are clearly specified on that page, which even includes a color-coded diagram showing exactly where to mount them, pictures, and instructions - is this the chassis you have? If so, you need a Pololu 3/8" ball caster or a Pololu 1" ball caster, depending on whether you want the motors under or over the chassis.