Summary: Let \(_R M^{l'}_n\) be a category which is equivalent to the category \(_RM\) of left \(R\)-modules. We define a functor \(F :{_RM}^l_n \to {_R M}^{l'}_n\) and prove that the functor \(F\) preserves products, direct limits, injections, surjections and total exactness. Finally, we show that the functor \(F\) is a left-adjoint of the inclusion functor \(I : {_R M}^{l'}_n \to {_RM}^l_n\). Hence \(I : {_RM}^{l'}_n\) is a reflective subcategory of \({_RM}^l_n\).