KHA Series, as a middle size, heavy size and adjustable type, can be controlled the velocity of a shock by adjusting the adjustment dial (to the left and right, each 180? ). KMA Series, as a small size and adjustable type, can be controlled the velocity of a shock by adjusting the adjustment dial (to the left and right, each 180? ). If a bumper head type is used, it prevents the bottoming phenomenon that may be caused at the end of a cycle. Therefore, stop collar isn't required.