Grotek pH Buffer #4 

We recommend calibrating pH testers weekly for readings you can trust.

It's best to keep pH electrodes wet, calibrate pH meters at #4 to give your pen a "slope" reference.

pH Calibration Solutions are available for all of your pH meters.

Each solution is made with superior quality ingredients and is conveniently color-coded for easy reference.

Be sure your meters are accurate by calibrating with Grotek Solutions.