This is now available in my Etsy store, along with a larger version covering larger screws: https://cmhprinteddesigns.etsy.com/

Update 27 Oct 2020: I made an edit to this thing to add a small change with screw threads in the back, and when I saved the edits, the thing somehow became visible only to me, showing a 404 for everyone else. Nothing I could do would get it to show up, and contacting thingiverse has resulted in no response. I've since had to repost it here.

Update 20 Aug 2020 - I'm a big fan of m750's remix because it has nuts press-fit in the back, and I have some SAE screws that get in amongst all my metric stuff, so I like to confirm if there's any question. I have printed several of that one, but realized that I wanted to have threads in my design as well. There's just enough room in the back - maybe not for press-fit nuts, but I can do printed-in threads. I've printed off the new one (see the silver print in the photos) and it works well. I did chase all of the threads with my metric tap set, but they didn't require too much cleanup after printing at 0.2mm. The originals without the threaded holes are still there as well.

Quickly sort and measure metric screws and bolts in sizes ranging from M2, M2.5, M3, M4, or M5 with lengths from 4mm to 50mm. Screw diameter sizing is a simple go/no-go clearance check which is faster than threading in a screw. Note that this doesn't tell you anything about screw pitch, but all of my metric stuff is standard coarse thread so I'm okay with this. If you want to confirm the exact thread, check out sneaks' original design with threaded inserts or check out registeredthing's remix with nuts as inserts.

Update 28 Feb 2020: Per a request I have uploaded a version with no keychain loop or back text. This is available under Metric screw measuring device-sanitized.stl in the Thing files.

Note about standard lengths

I've gotten several comments about the ISO standard lengths and how it goes up in 5mm increments past 20mm and so forth, and several requests to redo this with the standard lengths. There are already several remixes which have done exactly that. The problem is not every bolt and screw complies with standards. I have right here an M8x22, an M6x15, and an M4x13. If I had the markings on the "standard" lengths, it would be difficult to determine the exact length of those. Because of this, I have no plans to change Sneak's excellent original design and don't find it that hard to read. If you are certain you'll always deal with bolts which conform to the standards, then check out the remixes.