Just a guess, Alpha aluminum= 6061
ZR 9000= 7005 Oh yeah Don't forget that it's hardened with Zirconium!
It's hard to get by all the marketing jargen used to make something sound more than it really is, and I'm not trying to suggest one company does it any more than any other, or tries to mislead. They truly believe their product is better, because of the extra step they take. To me it's six of one...........