The li-Ning 99 td is used by world champion and Olympic gold runner up chen long. The li-Ning 99 td is part of the "air stream system series" which uses the wind tunnel structure which reduces wind drag by 8. 2 percent and increase the shuttle speed by 3. 1 percent. The iconic wind tunnel design minimize the formation of eddy during swinging motion. It prevents racket instability and also achieves more accurate dropping point. The 99 td is an ideal racquet for drop shot technique play. With added weight to its racquet head using the latest multi polymer carbon fibre reinforcing technology, players can maximise the advantages of g force, while optimise the gravity force to create exceptional power and speed. Through extensive research an development in nano science technology, g force provides players with the extra edge needed in their game. Air stream system unique patented air vents located at the top and/or bottom of the badminton racket frame reduce air resistance by an astonishing 8. 2 percent resulting in increased smash speeds by up to 3. 1 percent.