Review on Amlong Crystal Premium Optical Diameter by Dustin Miller

I have a double concave image to use with art to test accuracy of portraits. The double concavity gives you a virtual image as if you were looking at your drawing in a mirror, except it's not upside down. Don't ask me how it works, but it makes it easier for you to see what's "off". I also bought a double bulge just because it was included, but I've used it several times before to increase the fine print or add reference detail to a drawing. I don't know why, but I find it much more comfortable to use than a magnifying glass, perhaps because there's no interfering handle or frame. A very good buy. I'm glad I have both.