These values are pretty close, but inaccurate. I took 6 and placed them on my large Stanley level that was on the concrete floor and placed the small levels on top. You can see all level measurements in the picture. Of the 6 levels, 2 were nearly accurate, 2 were close but deviated noticeably, and 2 deviated significantly. They also varied depending on which side they were on. The pair had sides that were significantly more or less accurate than the other sides. Please note that the inner tube is not symmetrical. It is slightly curved and longer at one end than the other. The black lines mark the center of curvature, not the center of the pipe. While this does not affect accuracy, it can be a little confusing at first glance.
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