1.It has a soft shock absorbing effect because the self-pressure-regulation function. 2.The spring can reset the piston rod fast cause the perfect movement of the check valve. 3.It adopts horniness chromeplated piston rod, special sealing element. It can have a long and stable efficiency. 4.It can adopt fittings, such as orientation stop screw cap, setting nut, retaining plate etc. 5.The nonstandard can be also manufactured.