A flat, so called tipless quick coupling, so it does not “squeak” when connecting the oil. The flat quick coupling can be connected with one hand and is easy to keep clean.
Advice: do not connect the quick coupling under high pressure, by forcing it you will break the seals of the quick coupling and it will start to leak. If the connector does not engage under light force, remove the pressure from the cylinder or the hydraulic system of the ATV. You can relieve the pressure by loosening the connection, e.g. by opening the connection at the root of the quick coupling. Take safety into account and ensure that the cylinder is not under load. You can also put a rag over the joint when opening the joint.