Improve reaction speed and hand-eye coordination. Develop timing, hand speed and accuracy of movement. Build quickness and agility while increasing stamina.The absolute best equipment for developing speed, timing and accuracy. Both length and tension of the elastic ropes are adjustable and tool-free. Easy to mount on door frames with the Adjustable Door Frame Fixer. No damage to your door frame and no screw needed! This has made it the choice of professionals and that is the reason we are supplying these to world class health clubs, gyms, boxing clubs.