Check the listing for details. LM399 4-CH Voltage Reference Source 10V/7.5V/5V/2.5V For Voltmeter CalibrationyB. Condition: New. Listed at 28.29 USD. Accuracy: 0.0001(AD584), 0.00001(LM399). Warm Floating: 0.5ppm/℃(LM399),.