Medical Gas Pipe labels conform with the NFPA 99 2018 Health Care Facilities Code and CGA C-9 2013 Standard Color Marking of Compressed Gas Containers for Medical Use. Our pipe labels are designed to wrap completely around pipes ranging from 3/8″ through 2″ in diameter. Size M2 has two 4″ x 7″ markers per card. We recommend you use them on pipes from 1″ to 2″ in diameter. Size M3 has three 3″ x 3″ markers per card. Use on pipes ranging from 3/8″ through 3/4″ in diameter. These are adhesive backed markers that you peel and stick, all markers include arrows.