Sheared Witt Vectors

V. Drinfeld and E. Lau introduced a ``decompletion’’ of the ring of $p$-typical Witt vectors, following earlier work of T. Zink. The goal of this paper is to offer an exposition of this construction, which we call the sheared Witt vectors, on the category of rings $R$ whose reduction is a perfect ${\mathbb{F}}_p$-algebra.