# NMRA Standards Gauge for HO Scale



## bluenavigator (Aug 30, 2015)

Does it matter which version for the NMRA gauge to use?

I am considering to get one. 

The latest one is Mark IVb, I think. I am seeing other versions as well.


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## johnfl68 (Feb 1, 2015)

For HO, there looks like there is MARK III, IV, and IVb.

The main difference between the MARK III and IV is the location of the tabs and slots on the gage.

I am not sure about the "b" version of the MARK IV. I have not been able to find anything on that version.

I would assume that some minor change was made, to warrant labeling it differently.

For probably 99% use, any MARK III, or IV HO gage should work fine for you, but the IVb would be the newest.

But I am now curious as to what changed on the MARK IVb gage.

John


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## wvgca (Jan 21, 2013)

as far as I know, track and related spacings are the same on the 2/3/4 gauges, however the 4 is physically taller than the three gauge ... I _think_ the height difference is for the difference in standards between the actual prototype railroad 'classes' a class 1 line with modern equipment needs more tunnel height and width clearance for larger rail cars ... and the new type 4 / 4a standards gauge reflects this .. on the nmra site they have different clearance standards for old time, classic, and modern styles or era of desired layout ..it;s the S7 clearances standard


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## CTValleyRR (Jul 26, 2014)

No matter what version you get, you should really have at least one. There is no better tool for troubleshooting problems with track and wheels.

I honestly can't tell you what version I have, but I've had it for 15 years and never had an issue with it.


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