Railway Engineering
Track Gauges

Round (called Rollee Holders)
Little Cylinders of Accuracy

Railway gauges are not castings, they are machine lathed accurately using fixed dimension TanTung steel cutters. Each gauge is cut to dimensions that lay your rails at the perfect spacing to give you the best performance on straight and curved track.
These gauges are made of Lucite rod (in colors to identify rail size) so they do not short out the track. The gauges come four in a pack since we've found four to be the minimum number you need to lay track reliably.
For many years it was believed that track needed to be wider in the curves. This was never true. An accurate gauge that lays the rails with the correct spacing, doesn't need to widen in the curves. There is already plenty of room for play.
HO, for instance, is .650 (650 thousandths) and the wheels are .635 so this leaves a full .015 (15 thousandths) for play. A similar situation exists with the other gauges. Hand laid track, when done carefully, can result in far fewer derailment problems.

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N Hn3 Sn3 HO On3

Blue code 40 - Red code 55 - Yellow code 70 - Green code 83/100
Pick the Gauge you want and the Rail size

N____ Gauge Code 40 55 - -
HO___ Gauge Code - 55 70 83
HOn3 Gauge Code 40 55 70 -
Sn3__ Gauge Code - 55 70 83
On2__ Gauge Code - 55 70 -
On3__ Gauge Code - 55 70 83
Package of Four Rollee Holder Track Gauges Only $9.95