I was running the stock pulley when I was having the charging issues, it didn't rear its ugly head until night time when the lights and stereo were on, my car was running a little strange like it was breaking up so I bought the alternator pulley for 20 bucks and all my problems went away. The pulley is tiny in comparison to the stock and underdrive pulley, it measures out at 1 7/8" and required me to turn down .060" off the outside diameter of a 1" socket on a lathe at work to install the alternator pulley. I used my impact to tighten it down.