ACE rotary speed controllers are maintenance-free and ready to install. The braking direction of adjustable speed controllers with partial rotation can be clockwise, counterclockwise or in both directions. The outer body is zinc die-cast and the shaft is steel. The controllers control the opening and closing of boxes, covers or flaps. They can brake directly at the pivot point or in transmission with a pinion, so as to provide a smooth and regular movement. Sensitive components are protected against jolts. The harmonious movement process enhances the quality and value of the product. Particularly suitable for hatches, case closures, lids, for applications such as printers, copiers, furniture industry, etc.