This article is from the Model Trains FAQ, by Christopher D Coleman with numerous contributions by others.
O-27 Style
O-27 - 8 per circle
O-42 - 12 per circle
O-54 - 16 per circle
O-31 Style
O-31 - 8 per circle
O-54 - 16 per circle
O-72 - 16 per circle
Super O
12 per circle
 
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