Sn3.5, in some cases tends to be oriented toward the New Zealand Railway (NZR), New Foundland, Australia, Queensland and South African railways. Modelers of these railways on occasion may use narrower than HO track.

The term Sn3.5, this scale type, equates to Sn42, as an "either or" expression of types. Sn3.5 meets the Sn42 character of modeling as both utilize HO locomotives/rolling stock and On30 locomotives/rolling stock modifiable to Sn3.5's 1/64th scale. Mechanical power units and wheel sets are generally HO or HO equivalent in size in order to fit within the desired locomotive shell and compliment gauge. Kit bashing abounds making this scale a very cost effective type to model. Track, turnouts and crossovers are HO specific and very reasonably priced. On30 track appears to be more visually correct than HO. S scale structures are required. Creativity is a key word in describing Sn3.5 scale. Purist lean toward the narrow gauge Sn3, Sn2.5, Sn2, and proto version modeling as they are more singularly gauge specific, some requiring hand laid track etc.