These cylinders include a female quick disconnect fitting at the top of the cylinder. They are compatible with any hand pump or electric pump that has a male fitting at the end of the silicone tube. These fittings make it easy to switch out cylinders as you increase your size or needs. Most standard penis pumps do not include the necessary quick disconnect hardware to use a modular cylinder. In order to add a stand alone cylinder, you will need to purchase a pump accessory kit that includes silicone tubing and the necessary quick disconnect fittings.