There is a big difference between soundproofing (isolation) and absorption which does little to nothing in regard to transfer through walls.
If you are looking for absorption they'd be fine for hi mids and hi frequencies, but aren't thick enough to do a whole lot for low mids and lows.
If you are looking for isolation the only way to do that is with mass.
I probably wouldn't buy his product because he obviously doesn't understand the difference between soundproofing and sound absorption. Very misleading. They are making money by not only being ignorant, but selling a product that won't do what his site implies. They are basically selling you thick moving blankets.