New Hypro 2-1/2in Stainless Steel Glycerin Pressure Gauge 0-100 PSI Brass movement with phosphor bronze Bourdon tube. Stainless steel, 1/4in NPT, brass male connection. Black enameled aluminum pointer, white background and acrylic window, Glycerin filled, For use with air, gas, oil or water Not to be used Oxygen or Acetylene Glycerin fill protects the internal components from pulsation on spray systems