N-Scale Train Modeling is a hobby concerned with the recreation, display and operation of railway equipment in miniature. N-Scale is also sometimes referred to as "N-Gauge".
N-Scale is a group of similar dimensional relationships including (but not limited to) 1/160, 1/150 and 1/148. All share in common a railroad gauge (distance between the two tracks) of 9mm (0.354 in). The earliest model trains to use this scale were made by Lone Star in the United Kingdom in their OOO (Treble-O) line. Interestingly, the Lone Star models use a dimensional relationship of 1/152. The first models to use a 1/160 scale were made by Arnold of Germany in the 1960s. The most common dimensional relationship in the United States and Europe is 1/160. Japanese manufacturers make a mix of 1/150 and 1/160 products but for the most part use 1/150. Model manufacturers in the United Kingdom prefer 1/148.
When it comes to track, N Scale always uses a 9mm distance between the two rails. The track height, however, can vary by manufacturer and/or product. Common heights are 0.08 inches high (Code 80) and 0.055 inches (Code 55). For narrow gauge modelers, track is 6.5mm between the rails (Z-Scale), but the dimensional ratio of the models is still typically 1/160, 1/150 or 1/148.
Worldwide, N Scale is the second most popular model railroading Scale after HO, but in certain geographical regions (Japan in particular) it exceeds even HO in sales.