Refractor

Refractor: A parallel set introduced in 1993's Topps Finest. Only found in chromium sets, refractors look the same as regular cards, but they "refract" a bright rainbow when held under direct light, especially sunlight. They might be tough to spot at first, especially with the first couple years cards, but once you see one, you'll be able to spot others easily. In the last few years, Topps has added a notation on the back to specify refractors. Though now lumped in with all the other parallels, 1993 Finest Refractors are still sought-after, and their never-confirmed-nor-denied print run of 241 copies remains a benchmark for scarcity.