They are accessories of the hydraulic blowout preventer. They are necessary devices for controlling the pressure in the well to avoid well kick.

The choke manifold, kill manifold, and associated gate valve group form an integrated well control system designed to manage and regulate wellbore pressure during drilling operations. Manufactured in compliance with API Spec 16C, these manifolds provide controlled pathways for circulating drilling fluid, handling kick fluids, and executing kill operations. The choke manifold incorporates adjustable and fixed chokes for precisely controlling backpressure while flowing kick fluids from the well. The kill manifold enables high-pressure fluid injection directly into the wellbore for well control operations. The gate valve group, consisting of multiple manually or hydraulically actuated valves, provides isolation, diversion, and redundant shut-off capabilities for safe and flexible flow management.