THIS IS A LOT OF 3 EA  Oxygen flowmeters,  back  pressure compensated Puritan, used but in excellent condition, made in the USA

These oxygen flowmeters have a female DISS  inlet port at the back and a DISS male  port  at  the bottom outlet  with a barbed connector attached.  They have 50 psi power outlet check valve. 

This item may be subject to FDA regulations.