Lots of pool stores sell "Liquid Chlorine" that's 6%, same as Ultra bleach. In fact, exactly the same, except, perhaps for price. Then they sell the strong stuff. If it's in 5 gallon carboys it's also LC, but 12.5%. If it's in gallon jugs of 10% or 12.5%, it's usually badged as "Liquid Shock".

"Shock" is a HORRIBLE word to use as a noun for a pool chem.

Carl