Pur Gro pH Probe Industrial Replacement
$119.16 $148.95
These don't look like the ones from the hydro store because they are double-junction, flat surface pH probes typically used in chemical plants for process control. They last longer, stay cleaner and are built to mount in-line inside your GroBot Evolution. Cost a few bucks more, but these are the good ones. Proudly made in the USA.