These are replacement external O-Rings compatible with Parker Series 9 pulse valves and Ideal Vacuum High-Speed Pulsed Solenoid Valves. The external O-ring forms a vacuum-tight seal between the valve body, which contains the output orifice or nozzle, and the vaccum chamber or item under test. These O-rings are made of chemically-resistant Viton® for use in vacuum or mild to moderate chemical environments.

See drawing below for external O-ring replacement location.
_{Viton is a registered trademark of The Chemours Company FC, LLC.}