Unused Only tried on YONEX STB Innerwear/Underwear Size M (Soft Tennis/Badminton) [Women's][Pro Model][STBP1507] ¥10,560 (tax included) STB is high-performance underwear developed for all athletes, focusing on core (body core) balance. Based on the latest biomechanics, it achieves a core balance design centered on the pelvis for movement in three directions: front and back, left and right, and rotation. By effectively placing compression materials on the origin, insertion, and muscle recovery of muscles, it guides muscles and the skeletal system to the best position, maximizing the athlete's performance.