This 4-pack of interchangeable replacement Rollers heads has been designed to fit the Scholl Velvet Smooth Pedi Electric Hard Skin Remover. Use this refill pack to replace your existing worn out rollers with a brand new pack. Directions: 1) Make sure the unit is turned off 2) Press the eject button on the side of the unit and remove the existing roller 3) Insert the new roller into the unit by sliding in the roller from the top of the unit one side first and press it in all the way, then slide in the other side and make sure it clicks into place 4) Shake the unit gently to ensure the roller has been securely inserted Disclaimer: The ONE1X (TM) replacement rollers are in no way connected or affiliated to the trademarked manufacturing companies Scholl and Dr. Scholl. ONE1X (TM) is an independent manufacturer of quality replacement rollers.