The Six-One 90 we've all been waiting for. Quicker through the
 contact zone and offering a larger sweetspot.  Some subtle updates
 to the shaft design and a more open feel to the stringbed sets this
 latest version apart from its predecessors and provides a closer
 performance to its ProStaff 85 roots. At net the KSix-One feels rock
 solid and very precise. The sweetspot feels larger here than with previous
 Tour 90s, and our team found good targeting. On serve we found plenty of
 control. Pace and court penetration come from the player's ability to utilize
  the racquet's mass. The stringbed offers plenty of bite and we found some
 noticeable hop to kick serves. All in all a very impressive racquet that is a
 must hit for 5.0+ level players.

Pros that use this racket:  Roger Federer ..... Need we say more?

Locals using this racket:  Jorge Salinas ..... The back hand speaks for itself.