A barrel has an external metal cylinder and a plastic vessel. The external metal cylinder has a cylinder body, an open top and an open bottom. The plastic vessel has an inner space with a sealed bottom as well as a through top flange. The top flange of the plastic vessel is sleeved tightly into the external metal cylinder, and embedded into the internal curling portion formed by the open top of external metal cylinder. Moreover, the sealed bottom of the plastic vessel is extended into the open bottom of the external metal cylinder, and kept with a recessed spacing to the curling flange, while the bottom of the external metal cylinder is exposed. The barrel can be applied to toilet brush assemblies in order to reduce the manufacturing cost, prevent rust and facilitate the cleaning process with better economic benefits and applicability.