This short-range Hydrion MicroFine pH paper measures pH solutions in the alkaline range of 12.4-13.9 and offers clear bright single color matches at every .2 to .3 interval. Hydrion MicroFine pH papers are ideally suited to testing minute amounts of solution, only requiring 0.0001 mL for an accurate measurement. With a width of 5/32 in, Microfine pH paper also fit easily into small tubes.