Functions well for its intended purpose and could be worth $100 but for the following corner-cutting: (1) The listing claim that the tool is "1/8 Inch Heavy Gauge Steel" is incorrect, to be kind with the comment. The one that I received mic's out at 0.075 inches, which is closer to 1/16 inch than 1/8 inch (but still mostly enough threads to be useful if one is very careful); the "satin chromed steel" finish is nice, but stainless would have been timeless; printing rather than engraving of the lettering was not a high-quality idea; and the machining of the threads is not as perfect as required for a high-quality thread gauge.

To keep these critiques in perspective, this SAE thread gauge and it's two companion metric thread gauges from Ruelle are more useful and information-packed than any other thread gauges currently listed on Amazon. My rationale for that opinion is the rich set of thread pitches available with a set of all three gauges plus the inclusion of numbered tap drill bit diameter gauges. No other set comes close.

I believe that I perceive a certain proud but sad bit of American manufacturing history represented by these Ruelle thread gauges. According to my research, Ruelle Industries, Inc. was a tiny, family-owned manufacturer of these gauges located in a tiny township in Michigan, northwest of Detroit. I imagine that they "hung in there," slowly yielding ground quality-wise in a futile attempt to compete in a brave new market of $25 consumer-grade machine tools utilizing American-grade labor and materials. According to opencorporates.com, Ruelle Industries, Inc. became inactive and the corporation was dissolved in mid-2021, less than one year ago as of this writing. Thus I assume that the gauges currently for sale on Amazon are leftover stock. If so, it might be a good time to grab a piece of Americana. (The foregoing is nothing more than my experience with the product, ten cents of research and my personal conclusions. I have no other connection with or knowledge of Ruelle or the current sellers.)

Compact and effective for checking what screw you need.

READ THE INSTRUCTIONS.
This is not rocket science, but not knowing how to use it can make it useless.

This does not cover all possible screw threading's and is not metric. It does cover the most common SAE threading's used in the USA up to the limits of it's design.

This is made to test screws using the fingers only.
If you can't ***EASILY*** push it through one of the diameter sizing holes, then use the next hole size down.
If you need to use a screwdriver to turn a screw onto the threading, THEN YOU ARE DOING IT WRONG.
Don't over think it. Don't force ANY screw. Finger pressure ONLY when turning a screw.

If the screw threads are good, you should be able to screw it all the way through the steel plate ***BY HAND***.
If the screw goes ***almost all the way through*** by hand, and then stops, *** you will*** crossthread the steel plate if you use a screwdriver.

Somewhere I saw a 1 star review for one of these stating that it was useless because the measuring scale at the top wasn't accurate.
Just for a laugh, I measured mine - It was 1/32 of one inch off. People, that is totally insignificant! Screws aren't measured that closely except by NASA.
Some people just shouldn't be allowed to buy tools.

There is only one negative, and that is that that the markings are silkscreened on the steel. If you always keep it in a plastic bag, like the one that it came in, then it should last for years.

I use the gage to size up drill bits and hardware. It has never failed me.

For starters, the question everyone keeps asking - it's not 1/8" (.125") or 1/16" (.0625"), it's .075", aka 14 gauge steel sheet. Reading an Amazon description that seems thin, but it's perfectly usable. I also have a PEC Tools P/N 5114 screw checker for metric, and that's the same thickness for $10 more. In shopping around I don't think anyone makes a plate-style screw checker thicker than this unless it's plastic.

The notation on the front is a little odd, but understandable if you follow the included guide. PEC has a slightly easier to read layout on their version, but it's fine once you get used to it.

For accuracy, the threaded holes seem fine, although the "drills" clearance hole column feels a little oversized - don't have anything to measure them with here in quarantine. The plating process did leave some rough edges, though nothing like the flashing visible in another reviewer's photos.

As another reviewer noted, the "Protective Plastic Carrying Case" is simply a heavy Ziploc bag. I guess it could be helpful to protect the painted markings if you're tossing it in a toolbox and carrying it around everywhere? It's not like it needs a carrying case if you just leave it by your hardware drawers in the workshop.

Overall, it does the job I need it to do - tells me the size of an SAE screw. Don't expect it to clean rusty or mashed threads, that's not its purpose. The PEC Tools 5112 is probably slightly higher quality, but quite a bit pricier on something that I'm already having trouble justifying not just making myself.