Apacs Stardom Fierce Badminton Racket (5U) 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 Grommet Systems - This single-pass grommet holes construction provides more grommet holes, creating a high-performance stringing pattern that puts 7% more durability. Heavy Impact Frame - Strenghten at 10, 2 and 6 o'clock area of the head the racquet structure at the top of the frame allows the head to bend in a very controlled way and hold shuttles on the string bed for longer. The thin frame sides then allow the frame to flex more and transfer more energy to the shuttle. This combination allows you to smash with instant power. Reinforced Structure Frame - The new material is adopted in the frame in order to make the frame Ultra high Strength & Stiffness. As a result it can handle string tension of up to 38lbs.