refilter material made from hollow ceramic rings for trapping large dirt particles Directly after entering the filtration cycle, water is swirled through the hollow ceramic rings. Larger dirt particles thus sink to the bottom. The treated prefiltered water then continues its way through the other filter layers. EHEIM MECH is easy to clean and reusable. Prefilter material for large dirt particles Hollow ceramic rings Easy to clean Reusable Suitable for fresh and marine water