This device will reduce the speed of any regular, proportional servo. Connect it between your receiver and the servo (or servos) you wish to control for a more scale-like movement of flaps or retracts. Adjustable, it can be set to reduce the speed of your servo from super-slow motion to no speed reduction at all, with an almost infinite number of positions in between. Great for reducing or eliminating the tendency of a plane to “balloon up” when flaps are deployed. It can be used to control more than one servo by use of a regular servo wye.