Annular BOP The design and manufacture of Annular BOP is according to API Spec 16A standard. (1) Packing element is spherical or tapered type with massive storage volume, low operation pressure and excellent sealing function; (2) Bonnet is hemispherical-shaped, so there is no stress concentration on bonnet whenever bearing the pressure. (3) Bonnet and body are connected by a wedge block, so the pressure is evenly distributed; (4) Packing element is interchangeable with similar overseas products; (5) Use observation hole to check the life span of the packing element; (6) Piston is set in low position to have a shorter moving distance; Use wear ring on piston.