The biggest problem is it doesnt have any real marking that I know...I guess I'll see when i get it. However it was advertised as "custom". That was the only thing to describe it. Maybe it's the best option just to fill to 2500 and just go up in 100 psi increments. Just wasn't sure if there was a set number. However according to the replies it seems there is some mixed numbers. I reckon I'll just have to do my own testing and see what I come up with. I'll let you guys know the results. I might put this on the market soon, it was one of those impulse buys lol. Gonna play around with it a little first. Thanks for the help.