The AST (patented) is unlike any other swing trainer available. Designed to help experienced players perfect their bat skills and begining players to learn proper mechanics, a forward arm and outside swing barrier simultaneously eliminate both "dipping" and "casting". And, the height adjustable (24"-40"), movable arm positions the ball anywhere across the strike zone to realistically represent inside and outside pitch locations. Use the AST to build a compact swing, keep the "hands inside the ball" and develop a "quick" bat. Use it to increase bat speed and learn to "hit the ball where it's pitched". Includes a two-year warranty!