A device for dynamically attaching an elongated member to a vertebral member. The device may include a receiver with a channel configured to receive an elongated member. A fastener may secure the elongated member to the receiver. The receiver may further include a reservoir sized to receive a head of an anchor. The reservoir may be shaped for movement of the receiver relative to the anchor within one plane. This movement may accommodate spinal motion during flexion and extension of the patient. One or more dampeners may be positioned in the reservoir and contact against the anchor during the movement. The dampeners may provide resistance to the movement of the patient.