Tube is designed for the collection and storage of gas samples. The 125mL has a sidearm O.D. of 9mm, the 250 and 500ml have a sidearm O.D. of 13mm, but with the addition of a syringe sampling port for use with a CG-3022-05 or CG-3022-22 septa. Supplied complete with one CG-3022-05 red rubber septa.