A thermostatic element includes a metal cup that contains a material, which can expand and contract according to variation in its temperature, and is provided on an inside thereof with an insert that separates its inside volume (V1) into at least two cavities for storing the material. The thermostatic element also includes a piston which is axially reciprocally movable relative to the cup depending on whether the material expands or contracts. The insert includes at least one opening there through for enabling passage of the material between the at least two cavities.