TT Gauge (from “table top”) is a model railway gauge using a scale of 1:120 scale with a gauge of 12 mm between the rails. It is roughly halfway between American HO scale (1:87) and N scale (1:160). Its original purpose, as the name suggests, was to make a train set small enough to assemble and operate on a tabletop.
Mechanical Horse relevant products:
The Mechanical Horse Club 