- A thickening mousse that provides optimum body, texture and hold without buildup, RUSK® Thickr® Thickening Mousse delivers healthy-looking shine to fine, limp or lazy hair. Thickr Mousse contains naturally derived ingredients that dynamically bond to hair to thicken its appearance while moisturizing the hair. It’s concentrated, so only a small amount is required. It has a light, foamy texture, and is ozone friendly. Dispense upright, work into hands and distribute evenly through damp hair.