Micro Essential Lab CC-472E Color Coded Tri-Chek pH Buffer Set Chemvelopes Pack, 4.0, 7.0 and 10.0 pH Pre-weighted amounts of buffer powders in chemvelopes at three pH values: pH 4.0, 7.0, and 10.0 Quick preparation; powders dissolve rapidly in water to give fresh, reliable standards in just a few minutes Includes one dispensing vial of Hydrion color key buffer preservative Buffer preservative automatically tints each solution to its own value color