Stablcal Standards Calibration Kit, for 2100AN and 2100ANis Laboratory Turbidimeters. USEPA accepted for calibration purposes. Stablcal Stabilized Formazin Turbidity Standards are true Formazin dilutions developed for use in any turbidimeter. Kit includes 100 mL bottles of 0.1, 20, 200, 1000, 4000 NTU standard and a sealed vial of 7500 NTU standard.