This a Post Landing Ventilation (PLV) system duct from Apollo 11. Anticipating that as much as 48 hours might pass after splashdown at sea before recovery by U.S. Navy personnel and equipment, provisions were made to support Apollo astronauts inside the command module while waiting to be rescued. To insure breathable fresh air inside the CM a PLV system was available. Ventilation was through a valve system mounted on the forward bulkhead and opened and energized by controls on the Main Control Panel. Each astronaut was provided with a collapsible duct (breathing tube) to attach to the PLV manifold on the bulkhead and worn while seated using a head strap around the back of the head. The PLV ducts directed the flow of incoming air to the crewmen. The right- and center-couch crewmen use the short ducts and the left-couch crewman uses the long duct.
This is one of the shorter ducts flown on the Apollo 11 mission in July 1969. It is 3.25 inches in diameter and 15 inches long. Made of cloth with stiffeners every 5 inches, one end has a head strap and the other end an internal circumferential strip of Velcro for attaching to flexible cloth vents passing through the forward bulkhead. The ducts compress, accordion style, into small volumes and are stowed in one of the aft compartment lockers.
NASA transferred it to the Smithsonian in 1970.