"Drop-3" baseball bats are bats whose weight is equal to their length minus three. The "drop" is the relationship between the weight and the length of the bat. A bat that is 33 inches long is classified as a drop-3 bat if it weighs 30 ounces, while a drop-4 bat would weigh 29 ounces in this situation.
Drop-3 bats are required for all official high school and college play in the United States. Players cannot hit with lighter inches-to-ounce drop ratios. One of the major transitions in a young baseball player's development is moving to the drop-3 bat required for higher leagues. Making this transition is different for every player but necessary if the player wants to participate in high school and college baseball.
As players approach their high school years, some may want to continue swinging lighter bats. Other hitters may want the force that added weight adds to the contact with the baseball. The mass of the bat, the acceleration of the swing and the point of contact with the baseball are the three main elements that affect the force of the bat on the ball and how fast and far the ball is propelled. How much one element is sacrificed to the other should be considered when judging a young player's swing and deciding when the hitter moves up to the required drop-3 bat for high school.