We currently have everthing in stock that is for a 52" or smaller. The 60" and 72" should be arriving and making it through inspection by late next week.
It may however take a few weeks before your dealer has any of these in stock. If your interested in a set of these blades you may want to go ahead and order them from your dealer. Often a new blade design doesn't get it's own little slot on the dealer shelves as a "stocked" part until they are sure there will be enough demand for it.
Besides the extra long cutting edge what makes the Extreme Blade better?
I have bought from my Exmark dealer (last year) blades with extra long cutting edges and then sometimes there short edges I always liked the idea of the longer edge...