HO scale
Track
The "gauge" of a rail system is the distance between the inside edges of the railheads. It is distinct from the concept of "scale", though the terms are often used interchangeably in rail modelling.

HO scale

Section Title: Track
Table Section Text: The "gauge" of a rail system is the distance between the inside edges of the railheads. It is distinct from the concept of "scale", though the terms are often used interchangeably in rail modelling.

Track gauge	NEM	NMRA	Prototype gauge	Notes

16.5 mm (0.65 in)	H0	HO	Standard gauge	The most common gauge. The 16.5 mm (0.65 in) gauge is additionally used for standard gauge trains in British 1:76 OO gauge, and for narrow gauges by 1:64 Sn3½, 1:48 On30, On2½ and 1:22.5 Gn15.

12 mm (0.472 in)	H0m	HOn3½	Metre gauge and 3 ft 6 in (1,067 mm) gauge	Metre gauge is common in southern Switzerland, west and east Africa, parts of other countries and many tram lines. 3 ft 6 in (1,067 mm) gauge is used in southern Africa, Australia (Queensland, Tasmania, and Western Australia), New Zealand, and also non-Shinkansen JR lines in Japan.

10.5 mm (0.413 in)	HOn3	3 ft (914 mm) gauge	3 ft (914 mm) gauge once common to American mining railroads and shortlines, particularly in the Western States

9 mm (0.354 in)	H0e	HOn30	2 ft 6 in (762 mm) gauge	Typically used for lines in 2 ft (610 mm)-2 ft 6 in (762 mm) gauge. Uses commercially available N scale track.

6.5 or 7 mm (0.26 or 0.28 in)	H0f/H0i	HOn2	15 in (381 mm)–2 ft (610 mm) gauge	H0f uses commercially available Z scale track. Defined in NEM 010 for modelling 400–650-millimetre (16–26 in) gauge including Feldbahn and 2 ft and 600 mm gauge systems.

4.5 mm (0.177 in)	H0p	12 in (305 mm)‒15 in (381 mm)	"Park". Defined in NEM 010 for modelling 300–400-millimetre (10–15 in) gauge ridable miniature railways.

Sentence(s)

The rails are spaced 16.5 mm (0.650 in) apart for standard gauge tracks in HO.

final_sentence: The rails are spaced 16.5 mm (0.650 in) apart for standard gauge tracks in HO.