This is a brand new Aluminum alternator pulley with aluminum fan.  This set is designed for most original GM alternators as well as aftermarket 1 or 3 wire alternators.  Fits most popular GM applications such as Small and Big Block Chevy, Oldsmobile, Pontiac, Cadillac, Buick, and more.  The pulley diameter is 2 13/16" and comes complete with a dress up nose cover.  A nice finishing touch to upgrade an old or new alternator