These HI93701-01 packets are for use with Hanna’s compatible benchtop and portable photometers which follow the DPD method in which the reaction between chlorine and reagent causes a pink tint in the sample. The HI95771-01 are to be used with Hanna’s HI96771 (previously HI95771) portable photometer and follow a method in which the reaction between chlorine and reagent causes a yellow tint in the sample. Check your meter as to which reagent is required as they are designed to read different wavelengths and are not interchangeable.