Heads Down Training Glasses. Heads Down Trainers (HDT's) help promote proper fundamentals & body position in both hitting & fielding simply by controlling the players field of vision. Improvements in overall fundamentals will be seen instantly due to the player's focus & concentration on really seeing the ball. Endorsed by top college baseball coaches & Elite players in the US, Canada, as well as Major League Baseball, HDT's compliment instruction from coaches within team practices as well as individual use. Removable vision guides allow player's & coaches to wear as sunglasses anywhere (UV 400 protection, polycarbonate lens). Infield and Outfield: Instantly players will begin to see immediate positive results in the development of their fielding fundamentals. Simply by controlling the player's field of vision, HDT's promote proper body position & control when fielding balls. First Base and Catcher: Improves receiving skills & also helps to improve reactions & body position to balls in the dirt blocking for catchers and picks for first baseman. Batting: Head positioning & limited eye movement is key to seeing the ball clearly when hitting. Using HDT's during Tee Work or Soft Toss drills instantly starts to reinforce proper head position & visual tracking that will transfer directly to live batting practice & game situations. Removable Training Inserts: Head Down Trainers comes with one set of removable vision guides that you can re-use anytime. The vision guides are easily placed on the bottom part of the lenses. Colors: black/gray lens, black/blue lens, silver/gray lens.