Did you know that there are many different cylinders that are required to do the many different operations to make our lives easier? There are single acting, double acting, rephrasing, and telescopic to name a few. A single acting cylinder will have only one hose that will either extend or retract the cylinder. To do the opposite function, it requires another force such as gravity or a spring or another cylinder. The fluid in these cylinders only act on one side of the piston. A double acting cylinder is built similar to a single acting cylinder, but requires oil to extend and retract the piston. Double acting cylinders are required when there is no external force available. They also are used when a high force is needed in both directions. An easy way to determine if your cylinder is single acting or double acting is how many hoses are attached to the cylinder. Occasionally manufacturers will use the cylinder as part of the reservoir for their system, so you will see a second hose on the cylinder, the valve will allow the cylinder to build pressure on that end of the cylinder. A rephrasing cylinder is a form of a double acting cylinder, that has 2 or more cylinders that are plumbed in series or parallel, with the bores and rod sized such that all rods extend and/or retract equally when flow is directed and first or the last cylinder in the system. A telescopic cylinder is a form or both types of cylinders. The most common style is the single acting, they are commonly seen a lot on dump trucks, because you have the weight of the box of the dump truck as the external force to retract the cylinder when it gets extended. A telescopic cylinder is a cylinder that has consecutively small rods inside of each other to help extend the overall reach of the cylinder.