This is an air seal nozzle made from machined duralumin.
There is an O-ring inside for airtightness.
A general-purpose standard airtight O-ring (SS-055) is used, making repairs easy.
The nozzle outlet is slightly larger than other nozzles at Φ4.7.
The nozzle outer diameter varies slightly depending on the production lot, so please check the listed value to see if it is compatible with your chamber.