The "N-3" formula is for normal hair. The "C-3" formula is for color-treated hair.Chi 44 Ionic Power Plus - Energy Hair Thickener delivers the active ingredients deep to the hair follicle. Removes free radical scavengers. Promotes microcirculation of blood. Improves keratin structure density. Must be used every day to achieve optimal results. Vitamins and minerals to improve the keratin structure density while removing free radical scavengers which may contribute to thinning and hair loss. The treatment will help to promote microcirculation of blood to enhance the follicle that can contribute to grow hair stronger, faster and retain hair longer that ever before. Apply it to the scalp and leave in.