I need to calibrate my hanna combo meter, problem is nowhere in my country stocks it. So i figure i will order off ebay. Looking at those sachets as they would be easier/cheaper to ship and maybe clear customs a little easier Are they single application sachets? Cos damn that shit's expensive if it is. What's the difference between sachet and bottle? Do i have to use hanna fluids in order to calibrate properly? I think i may have made a thread very similar to this in the past.. Anyway yeah i never calibrated when i got it, been at least 6 months still no calibration. I dipped it in some ph 7 fluid and it read around 7.1, also looks in range compared to a liquid drop test but yeah EC could be right out for all i know..