Federer currently plays with the Wilson Prostaff RF97 Autograph , a 97 square inch tennis racquet with 21 @.@ 5 mm beam , 360 g weight , 331 swing weight and 16x19 string pattern ( all strung with overgrip ) . Since the 1998 Wimbledon Junior Championships Federer played with a Pro Staff 6 @.@ 1 90 BLX tennis racquet , which is characterised by its smaller hitting area of 90 square inches , heavy strung weight of 364 grams , and thin beam of 17 @.@ 5 millimeters . His grip size was 4 3 / 8 inches ( sometimes referred to as L3 ) . Federer strung his racquets at 21 @.@ 5 kg mains / 20 kg crosses pre @-@ stretched 20 percent , using Wilson Natural Gut 16 gauge for his main strings and Luxilon Big Banger ALU Power Rough 16L gauge ( polyester ) for his cross strings . When asked about string tensions , Federer stated " this depends on how warm the days are and with what kind of balls I play and against who I play . So you can see – it depends on several factors and not just the surface ; the feeling I have is most important . "