Apacs Z Series Force II Badminton Racket (4U) Isomectric head frame - Equalizes the length of main and cross strings in the stringbed, enlarging the sweet-spot for more consistent accuracy even on off-center hits. 76 Grommets system - This single-pass grommet holes construction provides more grommet holes, creating a high-performance stringing pattern that puts 7% more durability. Hi Modulus Graphite - The HMG is adopted in both sides of the frame in order to give strength and perseverance and to produce a high repulsion power. Triple Speed System Frame - The Triple Speed System is developed to achieve the combination of heavy smashes and speedy racquet handling. Resulting in instant power during smash and making a full swing easy during short range rallies. PreStrung with Apacs string (Strung with tension 23/24 lbs)