The invention relates to a device, in particular for the treatment of low-viscosity polymer melts, containing a vessel (1) with a stirrer element, the stirrer element (6) essentially comprising a support structure which passes through the vessel and on which surface formers (8) are arranged. According to the invention, the support structure is designed as a cage-like rod frame (7).This results in the following advantages:1. Owing to the now possible continuous wetting or wiping of the surfaces, encrustations and inhomogeneities are avoided.2. Due to enhanced cascading with weir plates, the residence time spectrum can be controlled, which likewise improves the product quality.3. The flexing of the stirrer element is reduced.