The REED R1404 is a ready-to-use pH 4.01 calibration buffer for pH meter and electrode maintenance, supplied in a 500ml (16.9 fl oz) bottle with a childproof cap and built-in viewing strip. It is color-coded red for quick identification and rated to +/-0.020 pH accuracy, with values traceable to NIST reference standards. A temperature-correction table on the label helps users read the correct pH value at different ambient temperatures.