Compound Gauge Refrigeration Ammonia 3-1/2 In. 30 in Hg Vac to 300 psi Connection Size 1/4 in NPT Connection Location Lower Smallest Graduation 5 in Hg 5 psi Accuracy +/-3-2-3 Percent Case Material Steel Case Color Black Socket Material Steel Tube Material Stainless Steel Lens Material Polycarbonate Operating Temp Range -40 Degrees to 150 Degrees F