The KRYTAC Rotary Hop Up Assembly is constructed of high quality polymer and features many user friendly updates to traditional M4 hop up systems. The rotary adjustment wheel is precise and definitive, each click position is numbered and the hop up offers a tactile and audible feedback when adjusting. The lever arm can be lifted upwards to give access to the hop up nub chamber for easy adjusting or cleaning. Also, the hop up nub is retained by the arm to prevent loss when changing barrels or hop up buckings.