The GD series multiple stage hydraulic cylinders are used where the stroke is large and the installing  distance or total length is too short (the stroke  may be more than the installing distance or total length). There are double acting or single acting. For the multiple stage hydraulic cylinders, the special piston seal has been adopted through oil port in cylinder and to reduce the inter-leakge in the piston seal system. Its features are reasonable in structure, reliable in operation, convenient  assembly and disassembly, easy in maintenance. The cylinders are widely used in engineering machinery, mining machinery, lifting and transportation machinery, environment protection machinery and traffic machinery (obstacle clearing vehicle) and so  on. Its working pressure, working stroke, installing distance, use stages, all kinds of stroke and rod diameter can be designed according to the user  requirements. Even the multi-stage equal-pushing-force cylinder design and manufacture is available.