The picture above shows the rails re-laid in the engine shed at Glynceriog.
These rails are set to the original GVT gauge of 2 feet 4 ½ inches.
Operational heritage narrow gauge railways of today predominantly are those with a gauge of 1 foot 11 ½ inches, (e.g. the Ffestiniog and Welsh Highland Railways. )
Other narrow gauge railways have a gauge of 2 ft 3 ins, ( e.g. The Tal-y-Llyn Railway and the Corris Railway
The Welshpool and Llanfair Railway has a gauge of 2 feet 6 ins.