Harley Benton Radius Gauge Notched 4-Set

Easily found in dense woodland if you miss a tree after throwing these. Also they are well disguised as some kind of gauge for guitars, so extra secret Ninja points for that.

Good tool for radius measurment. Not perfect machined but that's not a problem.

priced well and are good quality for the money. recommend if you need them but don’t want to pay big money for tools you might not use that often.

These radius gauges are every bit as good as the more expensive ones they sell at certain luthier's suppliers.

Good quality at a decent price.

Highly recommended!

You can measure easily the fretboard radius with strings on. If you move it little on the side you can measure the string radius near the nut or near the bridge. The different spaced string notches fit perfectly to my Gibson Leas Paul near nut and near the body.

Handy to check the radius of a fretboard without having to remove the strings. There's 2 sizes as well to check the first few frets and the 12+ in case of compound radiused fretboard.

These tools are cheap and precise. Though I considered buying expensive brand tools, I wanted to give these a try first, and it was a success! Additionally it looks like that the rough edge problem mentioned in older reviews has been eliminated, the edges are smooth and sounded. I totally recommend it.

The sharpness of the edges needs to be addressed before use. Otherwise, they do the job 100%.
ETA: After you've got a 100% perfect setup on your guitar (nut slot depth & perfect saddle height) what can you record with a fine-tipped permanent marker? Save yourself hours and hours of repeated guess work and eyeball calibration corrections. Printing measurements along the edges of the slots would make these immeasurably more valuable to first-time users.