The drop back rail for the Shocker RSX and Shocker XLS pushes the air source adapter(ASA) back toward the player. The rail also lowers the ASA approximately 1/2 inch which raises the marker slightly in the sight picture of the player. This repositioning helps players that have longer arms, are taller or just like a longer marker to feel more comfortable with the nimble Shocker RSX and Shocker XLS.