Check the listing for details. Biopharm Buffer Calibration Test 2-pack 8 oz (250 mL) pH 4.0 & pH 7.0. Condition: New. Listed at 17.99 USD. Biopharm Buffer Calibration Test Kit 2-pack 8 oz (250 mL) pH 4.0 & pH 7.0-For Precise and Accurate Calibrations, Designed for Hydroponics and Aquaponics- Ideal for ALL pH Meters Want that feeling of confidence from doing things right? Get our accurate, unbiased, independent and scientifically documented calibration standards and be sure your meter is working correctly. These buffer calibration solutions are suitable for the calibration of all pH meters. Each production lot is manufactured in our laboratory following carefully controlled written procedures and standardized against NIST standard reference materials (SRM) for high accuracy. The finished product is assigned a unique Lot number and expiration date. These products will have greater than one year shelf life when received. Convenient Waterproof Labels Suitable for ALL pH Meters FREE 'How to Use" sheet included Ideal for Hydroponics, Aquariums, Aquaponics and Pools Individually Bagged 250 ml (8 oz) Poly Bottles