Originally Posted by Povl Carstensen
It was me who first pointed out the difference in the groove. So to me, the K90 is still a good bet.
Federer and Wilson both went out of their way to say that Federer used a K90 when they were the current generation of racquets on more than one occasion. I don't seem to recall seeing anything like that happen with BLX Line of frames so I'm guessing that the K90 is probably his frame.