R-Hop is a popular modification in the Airsoft market in which a high-density rubber patch is installed in the hop-up window and then polished flat on the inside of the barrel to ensure perfect fitment. R-Hop improves the consistency of each consecutive shot, improves peak backspin and air seal, and provides the user with higher tolerances to imperfections in the projectile. All of these features combine to offer the Airsofter a higher-performing Airsoft weapon.