Abstract: Designed primarily for use in the production of heavy and medium oil in conjunction with a screw-type pump in relatively shallow or medium wells, the device comprises an inner mandrel within an outer casing situated below the pump and connected to the pump casing and prevents right-hand rotation in the event that the torque reaction of the pump increases due to sand, for example, and attempts to rotate the pump stator together with the production string tubing, but at the same time allows vertical movement of the string to take place for withdrawal purposes.