1.The circulation ports are opened by dropping a free-fall opening plug. 2.High strength retaining blocks prevent pre-mature closing and offer reliable performance even in deep wells. 3.Anti-rotation mechanism improves drill-out efficiency.

1.Used for two-stage casing cementing with well inclination less than 25 degrees. 2.The circulation ports are opened by dropping a free-fall opening plug. 3.After the stage collar is closed, the internal accessories will free fall to bottom, eliminating drill-out. 4.Full ID in the casing string is achieved after the internal accessories of stage collar free fall to bottom.