These IIAR-compliant pipe markers come with the traditional yellow background and are recommended for use in labeling ammonia piping and its contents. IIAR pipe markers should include: the marker body AMMONIA, physical state, pressure level, directional arrows, and an ammonia piping abbreviation. Style 1HV pipe markers measure 4 in. x 24 in., come with one marker per card and fit 8 in. or greater pipe diameter. Designed for use on rusty, dirty, wet or rough surfaces and can be used indoors or outdoors on horizontal and vertical pipes. Use with directional arrow pipe markers or banding tape.