Support bar is also called balancer.Its characteristic is the establishment of pressure energy reserve obtained by injecting high-tube together make up of a dependable seal system,which enjoys such advantages of big lift but small volume,big working stroke but small lift change,steady operation and convenient indtallation as compared with the mechanical spring. It is widely used for open of trunk compartment and rear trunk door of cars or applied in various kinds of modern storage rack,printing machinery,woodworking machinery and textile machinery etc.