The heart of any pneumatic highspeed handpiece is the turbine. The turbine is composed of a spindle/chuck on which is installed an impeller and a set of bearings. O-rings and possibly washers are used to seat the turbine in the head of a handpiece. The chuck holds the bur firmly in place; the impeller catches the air to spin the entire assembly; the bearings reduce friction and keep the entire assembly aligned in the head of the handpiece and the o-rings provide further stabilization. The handle is just that, a handle, through which run the air and water lines and possibly fiber optics.