Innovative design DF-6001 is an arc and horiztontal type with one hinge in one side and open in another side. Two pieces of insert plates and fixing bolts are used to fix and seal FOSC. The FOSC is suitable for protecting fiber cable splices in straight-through and branching applications. It can be placed in underground, aerial, wall-mounting, handhole-mounting and duct-mounting applications. Based on an advanced formula, the plastic parts are made of injection-molded, high-strength engineering plastic PC by numerical control equipment, therefore effectively prevent products from aging caused by coldness, heat, oxygen and ultraviolet radiation. The strong housing and main components provide fire resistant, waterproof, and quakeproof while protecting splice closure during pulling, torsioning and impacting. The DF-6001 has the following outstanding feature. Advanced internal structure design Easy to re-enter, it never requires re-entry kits. Fiber optic splice tray is designed in SLIDE-IN-LOCK and its opening angle is above 90 degree.Therefore it is easy and fast to increase and reduce FOST. The housing of FOSC is spacious in particular, while straight through fiber cable is for branching application, fibers not cut off are for straight-through after being fixed and winded, fibers cut off are for branching after fusion splicing with fibers of other branching fiber Cable. All of the above features make it easy and convenient for installation, maintenance and reuse. If required, the earthing deriving device can be installed on the housing of FOSC for deriving metallic parts of fiber cable for earthing connection. Pressure testing valve can be installed as well for pressure testing and sealing testing after injection air.