 Federer currently plays with the Wilson <unk> <unk> <unk> , a 97 square inch tennis racquet with 21 @.@ 5 mm beam , 360 g weight , <unk> swing weight and <unk> string pattern ( all strung with <unk> ) . Since the 1998 Wimbledon Junior Championships Federer played with a Pro Staff 6 @.@ 1 90 <unk> 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 <unk> ) . Federer strung his racquets at 21 @.@ 5 kg <unk> / 20 kg crosses pre @-@ stretched 20 percent , using Wilson Natural <unk> 16 gauge for his main strings and <unk> Big <unk> <unk> Power Rough <unk> gauge ( <unk> ) 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 . " 
