Sometimes, a set of digital calipers or dial calipers just won't work in the certain situations. With the advent of cheap digital calipers, it has become more reasonable to take these instruments into conditions where they may get splashed, knowing that they can be easily replaced should you accidentally drop them in a tidepool. Still, in some cases it's nice to be able to use a set of vernier calipers, especially when you know you'll be getting splashed or submerging the calipers. It used to be the case that you could find relatively affordable, high quality plastic vernier calipers. Plastic is nice since it won't rust, and you're less likely to shove the tips of the jaws through your arm accidentally, like you might with metal calipers. Unfortunately, you're hard-pressed to find a vendor for quality plastic vernier calipers these days. You can get stainless steel verniers, for a price, and they're still a danger to you when you're slipping and sliding around in the field. First of all, the build quality is as googd as you would expect. They're light and flimsy, and there is a ton of play between the main body and the sliding jaw. That's acceptable though, as long as they're somewhat accurate. Unfortunately, they're even a bit lacking in that department. The digital calipers do a perfectly acceptable job of measuring the I Button accurately and repeatably. Next dug out the trusty set of plastic vernier calipers (that you can no longer buy). These vernier calipers only have a resolution of +/- 0.05 mm, which is the typical standard for vernier calipers. They returned a diameter of 16.25 mm, as accurate as you can expect to be with these calipers (a reading of 16.25 or 16.30 would be acceptable).Lastly, the new "Cen-Tech" plastic vernier calipers come out. They have a resolution of 0.05 mm just like the vernier calipers above. They produced a measurement of 16.20 mm, and this measurement wasn't particularly repeatable. Sometimes it was as low as 16.15 mm.In use, these calipers have two glaring problems. 1. They're not particularly accurate, or repeatable. 2. They're a pain to read because of poor design. It's a bit of a chore to decide this though, because of the large gap between the ends of the vernier markings, which I've illustrated with the red lines.