Piston 2-oriented 3lai-oriented, piston and cylinder without touching, so without finishing the cylinder wall. End of the plunger is under  pressure to ensure the plunger cylinder with enough thrust and stability, plunger is thicker, heavier, and installation is easy to produce uneven wear, so the piston cylinder should be installed vertically. Installation when used to reduce weight and improve stability and plunger are made of seamless. This commonly used long stroke hydraulic cylinder machine tools, such as Plano, rail grinding, large broaching machine and so on.