Amlong Crystal Premium Optical Glass Double Convex and Concave Lens Set, 50mm Diameter, 3 Double Convex (20, 30, 50cm FL) and 3 Double Concave (20, 30, 50cm FL), 6 Piece Set

I got the double concave to use with art, to check my accuracy in likenesses for portraits. The double concave ends up giving you a virtual image, as if you are looking at your drawing in the mirror, except it's not reversed. Don't ask me how it works, but it lets you see what's "off" more easily. I also bought the double convex just because it was included, but I have already used it several times to magnify small print, or zoom in on a drawing reference detail. Don't know why, but I find it much more enjoyable to use than a magnifying glass -- maybe because there's no distracting handle or frame. Very nice purchase. Glad I got both.

These work well for my students and are large enough to hold and demonstrate the differences.

Used them for a lesson on light refraction for 5th grade students, worked perfectly.

These are amazing lenses! Perfect quality, worked great for my experiments and for a demo for my Physics course!

Is what it says it is. Very quick delivery to the UK