Design:Scrub the thick & hard calluses Foot files are safe and gentle, yet instantly eliminate thick, callused skin and produce baby-soft, smooth feet in seconds. Trust your feet to Coobi and transform your soles. How to Use: Our product has been developed to be used on both wet and dry skin 1. Typically, there is no need to pre-soak feet prior to using this tool, however, you also can have a warm water foot bath for 5~10 minutes to soften the dead skin and callouses, It depends on your situation. 2. choose the best foot file according to your varying heel conditions, control the force in case of injury of the foot. 3. Gently pass the tool back and forth on the area, slowly apply