Thank you for your order. Unfortunately, Nioxin gallon size are. We will replace it with four one-liter bottles at no extra cost. 3.75 liter = 1.00 gallon. 4.00 liter = 1.06 gallon. You will be getting a little bit more plus the added benefit of easier maintenance in separate bottles. Nioxin Cleanser System 1 is the shampoo component of the Nioxin System 1 process. Nioxin system 1 is a thinning hair solution tailored specifically for people with fine, non-chemically enhanced, normal to think-looking hair in the early stages of hair loss. Nioxin Cleanser System 1 gently cleanses the hair while removing build up and DHT (Dihydrotestosterone). Using the shampoo for thinning hair helps reduce excessive daily hair loss. Activ-Renewal in the thinning hair shampoo formula promotes a younger looking scalp complexion. BioAMP strengthens the hair by adding thickness from inside the cuticle. Nioxin Cleanser System 1 Benefits. Reduces excessive daily hair loss Removes toxins, build-up and DHT Improves the appearance of thinning hair Strengthens the hair Promotes fuller, healthier hair Moisturizes and energizes scalp and hair. The Nioxin Scalp Therapy is a conditioner for thinning hair that provides superior moisture and energizes the scalp. It is the conditioner part of each Nioxin system. Nioxin Scalp Therapy System 1 is for fine, natural (non-chemically enhanced) hair in the early stages of thinning. Nioxin Scalp Therapy System 1 is made with European botanicals and rich humectants. Proteins, vitamins and amino acids relieve tightness, itching, flaking and tension in the scalp. The botanical conditioner for thinning hair promotes volume and the healthy growth of fuller hair. Nioxin Scalp Therapy System 1 moisturizes the scalp and hair without over-softening or weighing down the hair. BioAMP thickens the hair from inside the cuticle while Activ-Renewal brings back the youth in your scalp. Nioxin Scalp Therapy System 1 Benefits. Volumizes and thickens hair Intensely moisturizes and nourishes scalp Soothes itching, flaking and tightness Lightweight finish Energizes scalp. Apply the shampoo for thinning hair to wet hair. Follow with Nioxin Scalp Therapy System 1 and Nioxin Scalp Treatment System 1. After cleansing with Nioxin Cleanser System 1, apply Scalp Therapy Conditioner to wet hair. Leave on for 1-3 minutes. Follow with Nioxin System 1 Scalp Treatment.