1/1 (One-of-One)

A unique parallel limited to a single copy.

A 1/1 (read "one of one") is a card with a print run of exactly one copy. 1/1s are usually a special parallel like Superfractor (Topps Chrome) or Black/Platinum (Panini). Because of their scarcity, 1/1s are among the most chased modern parallels.