I have a question that I dont think it was answered yet, We all know Federer's racquet specs are the same(or verry close) to the retail racquet but...his sticks have lead tape on the head and I assume they have silicone in the handle too. The retail racquet has foam filled handle so I will argue about the head only. If Fed sticks have the same specs with retails but with lead tape under the head grommet...this means that the weight difference(coming from lead) on the retail racquet,it is distributed on the upper side of the head(to mimic the leadtape)?that,to have the same swingweight of Federer's racquets. I am guessing if that difference in weight it is distributed in other parts of the retail racquet,this will bring another SW different than Fed's. My conclusion: the retail K90 or BLX90 is the same as Federer's racquet but with "lead tape" included.