American MarinePINPOINT pH Calibration Fluid 7.0 Packet

For roughly 1$, you can't get a more perfect solution for the price. I tested the Pinpoint pH probe with this solution and it returned an exact 7. It's counterparts (#10 and #4) are just as accurate...but since you will most likely purchase this one first, I will only comment here.

I love this stuff because you rip it open, calibrate your probe, throw the junk away and move on with your life. I must've bought of dozen of these for my Ca reactor (reef tank). Always have loved Pinpoint products.

good seller,fast shipper,will buy again!!

This is the industry standard for aquarists.

works great