Apacs Super Series GP 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. 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. Slim Box Frame - The Slim Box Frame provides smaller flat surface compared with an ordinary racket for better speed, fast swing-through, quicker maneuverability and power. 76 Grommets system - This single-pass grommet holes construction provides more grommet holes, creating a high-performance stringing pattern that puts 7% more durability. ZigZag Grommet - This increases the racket sweet-spot tension and reduce the likelyhood of the string tension loosing its strength, which will improve and maintain the consistency of Power and Control.