Characters: In the structure, it is divided into annular blowout preventer with spherical plastic core, annular blowout preventer with cone-shaped plastic core, and blowout preventer with tube-shaped plastic core. Annular bop top cap and housing are connected by bolts or claw blocks. Blowout preventer with spherical plastic core and dust-proof ring. Performance characteristics: reasonable structure, easy operation, long life of plastic core, adapt to a wide range, capable to seal pipe string with nominal paths from 0-dn in ans shapes, better performance by combining with ran blowout preventer in the use. -