Potassium hydroxide (also known as caustic potash, or potash lye).
KOH.
Used to make liquid soap. Comes in flake form and is 90% pure.

WARNING: Potassium hydroxide is a dangerous chemical.
You must wear safety glasses and gloves.
If you spill any on your skin, flush with cold running water until the stinging has gone. Vinegar and lemon juice will remove the sting too.

CANNOT BE SHIPPED OUTSIDE NZ.