Apollo Command/Service Module Oxygen System Fill and Vent Port, measuring approximately 5.5" x 2.25" x 2.25", marked at center with Fairchild Hiller/Stratos-Western part information: "Coupling, Vent, Abn, Liq Oxy, Control No. NAS9-150." A Beech Aircraft Corporation label is wrapped around the central tube. The port features a screw-on cap.