I gave it a 3 rating because no info was given about the piston on the documentation. I kept watching youtube videos on similar products but after compressing manually it lost the air pressure. I watched the video on 鶹 nothing about the piston. I went through the diagrams and saw the advise to make sure piston was set up properly. So I did that and was able to pump it and get the air pressure to 5 BAR. I was able to use it to clear the toilet quickly. Normally I would have given a 4 star but the frustrating problem to install would be a zero so 2 stars