Psc orbital. I had it on a buggy for a couple years and never had a problem. Took the buggy apart and the orbital layed around for 4 or 5 years and now I have it on a toyota and it dosent act right. Kinda stiff turning and when I turn one direction or the other it's like it keeps pulling the steering wheel around and I have had the tires turn a little without even moving the steering wheel. Gm stock pump. Thanks