Quadruple distilled Islay whisky: Usquebaugh-Baul
There was a whisky at Islay, distilled four centuries ago, that was quadruple distilled to 90% alc. vol.
It was said that more than two spoons of that whisky could kill a man.
Bruichladdich, according to the original recipe has recreated that whisky and responsibly has reduced it to 50% alcohol volume.
Bruichladdich X4 is the original spirit, unaged, that Bruichladdich released sometime ago.
After a time they have also released (surprise!) a new whisky that is called Bruichladdich X4+3
Osama, you would have done better asking it with water.