If your planning on keeping your cab on carpet, then 3'' rollers will probably be perfect. If your keeping it on wood, tile, or something similar, then it might be a little high, but I doubt anyone would notice. I used 2 1/2'' casters and they're not quite high enough, they do pretty much nothing on carpet and the bottom often scraps when its rolling on concrete/wood/tile. Since I don't move my cab, they work fine for me.