Original JUWEL fitting rings are ideal for ensuring that your JUWEL light units remain 100 % water-proof, even after you have replaced the fluorescent tubes. They were designed specifically for aquariums and are VDE certified for this type of use. Although high-quality materials are used, JUWEL fitting rings will suffer natural wear and tear over time. For this reason, we recommend that you change your fitting rings every time you change your fluorescent tubes.