NOVELTY - The vessel has a metallic liner (200) constructed from a metallic material. A portion of an inner surface of a polar boss neck region (304) is attached to a portion of an outer surface of a liner neck region (208). A longitudinal passage (308) is formed within the polar boss neck region that is coaxially aligned with a liner orifice (204). A polar boss annular flange (312) covers a portion of a liner polar region (212). A polar boss (300) is made of material with static strength, fatigue strength, endurance, chemical and/or corrosion resistance greater than that of the metallic material.    USE - Composite metal lined over-wrapped light-weight and strong pressure vessel for use as a bladder-type hydraulic accumulator (claimed) for use in different industries for storing fluids i.e. fuel for powering fuel cell vehicles e.g. aircraft, launch vehicles, and spacecrafts. Can also be used for storing gases such as compressed anesthetic natural gas (CNG), hydrogen and oxygen in a hospital and a dental office and for holding chemical liquid nitrogen, liquid helium, and cryogenic fluids in research laboratories.    ADVANTAGE - The vessel has high static strength, high fatigue strength and high endurance level, and ensures better chemical and/or corrosion resistance effect of a pressure vessel orifice region by attaching a polar boss to the liner material so as to avoid accidental over-pressurization phenomenon of the vessel and reduce fatigue level due to repeated loading and unloading of the vessel, environment-assisted stress corrosion, stress rupture from sustained loading, incompatibility between different materials for a fitting and a port, and degradation defects of material's strength over time, and/or a combination. The vessel is formed with a large port opening so as to install a bladder in an easy manner and accommodate the bladder with greater wall thickness with low permeability of the stored gaseous content so as to prolong service for the bladder.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for reinforcing a neck region of a composite overwrapped pressure vessel.    DESCRIPTION OF DRAWING(S) - The drawing shows a partial cross-sectional view of a pressure vessel without a plug or adapter fitted onto the orifice.    Metallic liner (200)    Liner orifice (204)    Liner neck region (208)    Liner polar region (212)    Polar boss (300)    Polar boss neck region (304)    Longitudinal passage (308)    Polar boss annular flange (312)