Roll Style Medical Gas Pipe Markers 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. Self-Adhesive Medical Gas Markers were designed to wrap completely around pipes ranging from 3/8" through 3/4" in diameter. Rolls contain 100 markers at 3" x 3" each. These are adhesive backed markers that you peel and stick, all markers include arrows.