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The annular BOP designed by our company is compact in structure and can seal square drill pipe, drill pipe joint, drill collar, casing and cable in various shapes and sizes.And provides a constant pressure control when the drill stem is operated.Annular BOP has two kinds of spherical and conical, spherical BOP has a bolt-type roof and wedge-top two.They are circular blowout preventer, compact and light weight for air transport, and can work under low temperature.