Set Turbidity Standards T-CAL (5, 20, 800, 4000 NTU)T CAL Turbidity Standards are stable Formazin standards prepared in ready to use concentrations to ensure accurate turbidity measurements. All concentrations are verified to meet tight quality control specifications, are EPA & ISO compliant for reporting purposes and are guaranteed to save you time. This set delivers all of the concentrations needed to calibrate and verify the TB 350 IR Portable Turbidimeter. The standards are supplied in sealed