Read the review by throwholics.com!

The Aerojav is used as both a competition and training device for javelin throwers. Currently USATF has adopted the Aerojav as the official javelin event for boys and girls ages 11-12.

For training purposes, the Aerojav can be a good tool for helping javelin throwers  learn the technical aspects of the throw. Because of its light weight (450 grams) the Aerojav is highly responsive to mechanical flaws in the throw and allow for more training throws than the heavier javelins.