Superior hard skin removal and a smoother finish with only one roller head * 2 in 1 system roller head for softer & smoother feet effortlessly with just one roller head*. *vs Scholl Regular Coarse roller head 1 File & Smooth 2 in 1 with one roller head 2 Safety Stop Technology™ that locks the roller head still if too much pressure is applied to prevent injury 3 Four AA Batteries File & Smooth 2 in 1 Roller Head: Ensure that the roller head is securely inserted into the unit. Turn on and place on dry (or wet), clean feet to effortlessly buff away unsightly tough, dry skin; remove roller head and flip 180° then gently smooth the treated area for a smoother finish.