This kit provides calibration buffers and a protocol for producing a range of accurate calcium concentrations for the calibration of fluorescent Ca2 indicators (1,2). This product contains 50 mL each of components A and B:    Component A (zero free Ca2 ): Zero mM CaEGTA (10 mM K2EGTA,100 mM KCI and 10 mM MOPS, pH 7.20)    Component B (40 uM free Ca2 ): 10 mM CaEGTA (10 mM CaEGTA,100 mM KCI and 10 mM MOPS, pH 7.20)    Colorless liquids  Store at 4°C  Preservative-free, use within three months of receipt