"Hot PBW" - that's not exactly specific?
I have some PBW & it has no declaration of the contents & does not mention temperature except to specify 100 - 160 F (about 60C for the enlightened) which is nowhere near sufficient to achieve sanitation by temperature exposure.
Apparently the item to be cleaned & sanitised should be exposed for 25 mins. So how do you do this - fill every keg????
If the PBW is caustic based this is potentially dangerous but no warnings are provided.
I doubt this stuff would meet labelling requirements in any civilised country.
BTW most of the world went metric before the end of the 70's. My kids do not know what an once or gallon is.