Fits my 2006 Chevy 2500HD 6.6L perfectly. Installation time was 2 hours. A special tool was required - a puller/pulley pusher. I got one for $17 from Harbors loader tool that comes as a kit and has a two-piece cup to wrap around the pulley, a custom bolt, and a bushing to hold the cup together. Without this it would be impossible. So if you plan to do it yourself, which is easy if you have the right tools, I would recommend ordering it here or sending it to the port. This is a NEW acdelco unit,