Brock String - Vision Convergence Training Tool - Train Vision, Improve Strength & Athletic Performance, and More! IMPROVES CONVERGENCE & PERFORMANCE: Convergence training using a Brock String can be useful for convergence insufficiency, as well as strength and athletic performance. SPORTS PERFORMANCE: With a 6-foot long string and 5 tight-fitted beads, this Brock String is great for training the eyes in sport-specific positions  giving you the ultimate athletic edge. EASY TO USE: You can use Brock String right from the comfort of your home with a very short learning curve involved. HIGH QUALITY: This Brock String is designed with an extremely high quality, and highly durable string and beads. Instructions Included You can return this item for any reason and get a full refund: no shipping charges. The item must be returned in new and unused condition. Go to Your Orders to start the return Print the return shipping label Ship it!