The dual-precision heads have slots to catch the normal hairs , and holes to catch the shortest stubble Designed to follow the contours of your face 2 dimensional technology that allows the razors to pivot in a circular motion and tilt inwards; Its system adjusts easily to every curve, minimizing both pressure and irritation For maximum shaving performance, it is recommended to replace your shaving unit once every 12 months Rotary head replacement For models 1150, 1180