Indigo® pH 10-13 medium to strong alkaline solutions; only $5.95 /50 strips.
They can be used to test your aquarium pH increaser solutions made from NaOH (lye). You can also use it for science fair experiments to test the buffering capacity of milk of magnesia which is used to reduce heartburn (indigestion) due to excess stomach acid production or to measure chlorine bleach which is in the range of 11-13..
Test Strip Documentation
|Stability Statement||Certificate of Analysis|