TT-gauge ( Table Top ) is intermediate between HO and N in size, with a scale of 1:120 and 12mm between the rails.It is a good choice for layouts that do not have enough space for HO, but do not desire to work in a gauge as small as N. RR-Track currently has one two-rail TT-gauge track libraries available for the layout designer, from Pilz.
Z-gauge is the smallest gauge currently available for the layout designer, with a scale of 1:220, and 6.5mm between the rails. It is a good choice for coffee table layouts, or layouts within layouts that are supposed to depict a model train. RR-Track currently has one two-rail Z-gauge track libraries available for the layout designer, from Märklin.
Click on the links at the right to see the contents of the TT and Z gauge track libraries.