Rams are either single-acting or double-acting. Single-acting sees gas fired into the bottom of the ram, pushing it out. It then uses some form of mechanical return, either a spring inside the ram or, in most roboteers' cases, bungee cord to pull down the flipper arm, thus pushing the ram back in.

Double-acting rams use gas to both extend and retract the ram. For retraction, gas is fired into the top of the ram, pushing it down, while the gas already in the ram from firing it is pushed out and exhausted into the atmosphere. This means you don't need a spring or bungee cord to bring the ram back down. But one downside is that you're effectively using almost double the gas for one flip which, if you have a limited supply, can hinder the usefulness of your weapon.