All YELLOW JACKET® gauges feature bold high-visibility dials with colored temperature scales for easy reading. And with Flutterless technology, surge protector minimizes the needle pulsation for improved accuracy. 1/8" NPT connection. 3-2-3% accuracy. Features retard protection to 350 PSI. Features retard protection to 500 PSI. Calibration traceable to NIST standards Red Pressure Gauge (Picture for reference only) Size - 2 1/2" Pressure Scale - 0-500 PSI Gauge Scale (Refrigerant) - R-12, 22, 502