The purest of pure GOLD tops off at 99.999% (0.001 is some other shit) AKA: Five nine! Therefore, something that is staight up, maxed out to the tits, top of the line is 'The five nine' or 'the 5 9' if you don't wanna spell that shit out.
Yo ma'fukka, check out this prime chronic I be rollin'. That shit's the FIVE NINE, nigga!
Oh my gosh, fellas! Look at the kaboose on Sally. I dare say it's five nine quality SHIT! Blah-DOW!