I have the D'Addario version and it's great. I've had cheaper ones too but their accuracy is hit and miss. And sometimes I'm happier with standard 6" steel engineers rule.
The perfectionist in me is bothered by that one. I like that they include the line thickness BUT it looks like you should read to the bottom of the line, but you should in fact read at the top. By that I mean, if the bottom of the string is at the top of the line, the string height is as indicated. If the bottom of the string it to the bottom of the line, your reading is 0.005" smaller.
For those of us with metric gauges, the line height is 0.25 mm, as is also the case for steel rulers with 0.5 mm divisions.
I have a few fancy gauges but never use them.
I use the strings (depressed at the 1st and 15th frets) for setting the neck bow, and a standard small ruler in 64ths for bridge and pickup heights. Easy peasy.
Thanks Dr.Kev I used my points and got it free !!!