The on-a-roll format of these markers allows them to wrap completely around 3/4" piping. The self-adhesive 3"x 3" markers feature direction flow arrows with 1/4" high characters, creating four lines of easy-to-read text on each individual marker. Medical gas piping must be labeled by adhesive markers or stencils that identify patient medical gas, the support gas, or vacuum system. Seton's medical gas pipe markers comply with the National Fire Protection Association Standard (N.F.P.A. 99C- Section 4-18.104.22.168)and the Compressed Gas Association Standard (CGA C-9 Section 4.1).