User blog comment:Zilla4444/AD upgrade for Chalice of Harmony/@comment-4652200-20120610204222/@comment-4652200-20120614191956

Blitzcrank 980base mana @18lvl + 216mana from Expanded Mind + 500mana Frozen Heart + 1350mana Manamune = 3046mana

2% of 3046mana = 60.92 amror pen + 20 from the passive = ~81armor pen

(+6 armor pen from offense tree and some 10-15 armor pen runes you get 97-102)

Oh and mages and AD carries got under 80 base armor @18lvl...

45 armor reduction which requires 3 attacks to take effect and costs 65 more gold

with you get 25AD more and 30% AS but you don't get active, mana reg, 15CDR and 30MR

and the components are much easier to farm for since there is no BF in the recipe