Baseball bats are measured using their length to weight ratio, a negative number that represents how many ounces a bat weighs compared to it's length in inches. For example, a 32 inch bat that weighs 28 ounces is a - 4. The largest ratio is in the range of -12 (for little league bats), while college and high school bats are restricted to a - 3. These restrictions are for safety reasons - a college or high school player swinging a very light bat (- 4 +) would simply have too much power and could pose a danger to other players on the field. Make sure to check the regulations of your league before buying a baseball bat!