Below is a list of Hydrolic Cylinders manufacturers from Rockford, Illinois. Hydrolic, or hydraulic cylinders, are devices used to convert pressurized fluid into mechanical power in the form of linear force or movement. A simple device, hydraulic cylinders are usually made up of two main parts: an outer cylinder barrel containing hydraulic fluid, and a hydraulic piston which is connected to a rod which moves it up and down inside the barrel. The distance that a piston travels with the cylinder until it is fully extended is known as its stroke. The length of a stroke is often used to classify the cylinder and this length can range widely from less than an inch to several feet in length in relation to the power required.