VitaLink pH Down EasyControl  is a concentrated acid (25% phosphoric acid) which can be used to adjust the pH of nutrient solutions.

Use in small controlled doses to lower the pH of nutrient solutions. Mix thoroughly and measure with a calibrated pH meter to attain the desired pH reading. Ideal for adjusting smaller volumes of nutrient solution.

Available in 250ml and 1L bottles.
Also available in pH Down which is a more concentrated solution ideal for adjusting larger volumes of solution.