N-gauge 5.5 mm (scale 2'9") diameter 3-hole disc w

For prototype information, please see the notes I have written for the non-caged set of similar wheels. Although this model only gets you 4 axles instead of 8, it shows what a difference caging makes to the price, with only having one "part" to handle and clean after printing. Please remember that it will be a bit fiddly to break the cage apart and not damage the wheels getting them out, and they may need a little more cleaning than if they had all been printed as separate parts. 
UPDATE actually it makes cleaning them a bit easier, as you brush them all at once from various angles still in the cage. The cage also breaks apart fairly easily using two pairs of tweezers.