Sper Scientific Differential Monometer, 0-15 psi Comes with a N.I.S.T. Traceable Certification 0-15 PSI with High accuracy of 0.3% fs at 25C Repeatability: 0.2% (max 0.5%) FSO Combined linearity and hysteresis: 0.2 (Max 1.0%) FSO 11 Units of measure; Backlit display