Duo contains cleanser and conditioner. Nioxin System 1 Cleanser helps to remove follicle-clogging sebum, and environmental residues from the scalp and hair. Cleanses to provide thicker-looking hair. For normal - thin looking, fine, natural non chemically treated hair. Nioxin System 1 Scalp Therapy is a lightweight conditioner that helps provide hair resilience and moisture balance control for normal to thin-looking hair. For normal - thin looking, fine, natural non chemically treated hair.