s: Powder buffer solution provide long shelf life and stability and are ideal for low volume use. Each pack makes 250mL of buffer solution. It provides indefinite or long shelf life and stability, ideal for low volume use. It"s lightweight, inexpensive and takes up very little space. These buffers are accurate to within 0.01pH units @ 25C and remain stable over long periods of time. Put into solution only what you need, when you need it. Features: 20 packs of popular pH buffer solutions, 10 packs pH 4.01 and 10 packs pH 6.86 Simple to use. Just add 250ml per powder packet Powder has an indefinite shelf life Easy 3-step procedure is written at the back of the packet Specifications: Each Pack Volume: 250 ml. Each powder packet/sachet makes 250ml of solution (when mixed with distilled or deionized water) Accuracy: 0.01pH at 25C Size: 7.5x 6.5cm/ 2.95x 2.56" Quantity: 3 Pcs/1 Set Note: 1.Transition: 1cm=10mm=0.39inch 2.Please allow 1-3mm error due to manual measurement. pls make sure you do not mind before you bid. 3.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you No Retail Package Package Contents: 10 x pH 4.01 Calibration Powder 10 x pH 6.86 Calibration Powder About shlpping: All items will be shlpped within 3 business days after the payment is received. Most times you will receive them within 8-12 days then. The specific delivery time is depend on circumstances.Any questions, please feel free to contact us During the shopping process, if you have any questions, please feel free to consult us, we will reply you within 24 hours, wish you a happy shopping Thanks for your cooperation and we'll make you feel satisfied.