The box body and base are sealed with hoops and rubber. The closure casing is made of quality engineering plastics, and of good performance of anti- erosion against acid and alkali salt, anti- aging, as well as smooth appearance and reliable mechanical structure. The mechanical structure is reliable and has the performance of resisting wild environment and intensive climate changes and serious working environment. The splice trays ( FOST) inside the closure are turn-able like booklets, and have adequate curvature radius and space for winding optical fiber to make sure the curvature radius for optical winding 40 mm . Each optical cable and fiber can be operated individually. The product can be opened again and reused after installation.