Ensure a proper seal when servicing the A/C system in your vehicle to keep refrigerant from leaking out. The A/C line o-rings seal the system off from the outside air to keep out moisture and keep refrigerant in. This 17x2mm o-ring is used in various locations throughout the system, please check for proper application before ordering. Recommended to be replaced any time a line or component is removed from the A/C system.