To be honest, I really don't understand what these are.* But it makes me happy whenever I find something on the internet that the internet doesn't fully explain to me. It makes me believe there are better things to come.
$10 at ReForm School
*(from the site) Optical Fun by Werkhaus are up-to-date designs of traditional optical amusements... The Optrixx is a looking eye in classic camera shapes (pre-assorted with Hassleblad, Kodak, Leica, Nikon, and Ziess Ikon). Look through and see objects reflected hundreds of times or hold over your camera lens for amazing effects (we've tried it, it really works!)