1.Light-weight,high strength Base on the nature of construction work,the hydraulic piston arm need to suit for high strength,high using frequency,high fatigability.to promise the sability and reliablity of application. 2.the seal system select the excellent seal kits from japan and germany.adopt the advanced physical design, 3:adopt the good-quality alloy honed tube,though cold-drawing and rolling,to reach an excellent toughness and surface hardness.improve the wear-resistance. 4.piston rod middle frequency induction hardening and tempering,chrome plated on rod surface to improve the anti-rust ,wear-resistance and anti-scratch property. 5.safety/cushioning fuction The inside of cylinder set up an cushioning device in the end of stroke,it can absorb the juge inpact.