Easy to use-no need to measure, just mix each pack with 250mL of distilled water. A total of 15 packs-the kit includes 5 packs of 4.01, 5 packs of 6.86, and 5 packs of 9.18 calibration solution powder to meet all pH requirements. Designed for portability-a single size pouch can be tucked in a drawer, bag or suitcase for use while traveling. Save time and money-by mixing the powder with a can of distilled water, you can keep them longer and easier to obtain without adding packaging! Wide range of applications-ideal for testing the pH balance of drinking water, swimming pools, aquariums, RO systems, spas or hydroponics. If you have a swimming pool, aquarium or spa, you will need to conduct a pH test regularly. However, troublesome liquid solutions may not provide you with the accuracy you need. Let go of the measuring cup and choose the convenience of pre-measurement. specification: ✔5 * 4.01 solution (potassium hydrogen phthalate) ✔5 * 6.86 solution (mixed phosphate) ✔5 * 9.18 solution (Borax) user's guidance: Step 1: Pour the powder completely into a clean 250mL glass beaker. Step 2: Add 250mL of deionized water (or distilled water) to the beaker. Step 3: Stir until the powder is completely dissolved. Step 4: Calibrate the pH meter according to the Esee pH meter calibration procedure (for Esee PH meter: B01LWMJVPG) Note: Not drinkable!