An apparatus for anchoring a rod to a bone fastener in a spine stabilization system. A first resilient insert may have two deflectable arms and a first channel formed therein. A second resilient insert may have two deflectable arms and a second channel formed therein. A cylindrical body may have a passage, wherein the first resilient insert and the second resilient insert have a width greater than the inner diameter of the cylindrical body when the first resilient insert is in a neutral state. Advancement of the first resilient insert or the second resilient insert into the passage deflects the two deflectable arms inward, causing the width of the first or second channel to decrease, and inhibiting the first resilient insert or the second resilient insert from moving relative to the cylindrical body.