User blog comment:Ziver7/My Heimerdinger Rework/@comment-94.145.98.40-20120712210056/@comment-4680018-20120713001244

If you rank up your turrets, you have a max stockpile of one turret until you level up UPGRADE!!. Once you have UPGRADE!!! you can have two turrets on the field and have a max stockpile of two turrets.