The invention relates to a cosmetic product refill (20) for a hair treatment device (1), comprising an applicator member (26) impregnated with an anhydrous composition, notably an oil, wherein the applicator member has a density of between 0.11 and 0.25 g/cm3 and the anhydrous composition has a viscosity of between 100 and 600 centipoise, preferably between 100 and 500 centipoise, at 22° C. The invention also relates to a hair treatment device provided with such a refill.
