The slide and barrel has 2 compensation slots for reduced recoil and muzzle rise Gonzalo. Better picture here : google.com/search?q=compensated+glock+vs+non+compensated&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi084eb7e3cAhVH11MKHSTGCrIQ_AUICigB&biw=1280&bih=6