A coupling assembly used to selectively couple a bone screw having an elongate shaft and a head to an elongate rod, the coupling assembly comprising: a coupling element having a top, a bottom, and a central axis (A c) extending substantially centrally through the top and bottom, wherein a portion of the top of the coupling element defines a saddle with a first side having an exterior surface and a second side having an exterior surface, the saddle defines a rod receiving channel with a longitudinal axis (A L) substantially transverse to the central axis (A c), wherein at least one of the exterior surfaces (144, 148) of the first or second sides of the saddle is angled with respect to the longitudinal axis (A L); and an outer housing having a first slider comprising a body and first and second spaced legs, the body configured to slide substantially parallel to the longitudinal axis (A L) longitudinally, toward the central axis (A c), from a first position where the saddle is substantially open, thereby permitting ingress or egress of the elongate rod with respect to the rod receiving channel, to a second position where at least one of the legs (214, 216) frictionally engages the angled the respective exterior surface (144, 148), biasing the respective side (142, 146) of the saddle toward the longitudinal axis (A L) to engage the elongate rod, thereby substantially retaining the elongate rod therein the rod receiving channel; characterised in that the outer housing further comprises a second slider, oppositely disposed from the first slider, wherein the first slider is configured to slide toward a midline portion of the coupling element from a first direction, and wherein the second slider is configured to slide to the midline portion of the coupling element from a second direction. a coupling element having a top, a bottom, and a central axis (A c) extending substantially centrally through the top and bottom, wherein a portion of the top of the coupling element defines a saddle with a first side having an exterior surface and a second side having an exterior surface, the saddle defines a rod receiving channel with a longitudinal axis (A L) substantially transverse to the central axis (A c), wherein at least one of the exterior surfaces (144, 148) of the first or second sides of the saddle is angled with respect to the longitudinal axis (A L); and an outer housing having a first slider comprising a body and first and second spaced legs, the body configured to slide substantially parallel to the longitudinal axis (A L) longitudinally, toward the central axis (A c), from a first position where the saddle is substantially open, thereby permitting ingress or egress of the elongate rod with respect to the rod receiving channel, to a second position where at least one of the legs (214, 216) frictionally engages the angled the respective exterior surface (144, 148), biasing the respective side (142, 146) of the saddle toward the longitudinal axis (A L) to engage the elongate rod, thereby substantially retaining the elongate rod therein the rod receiving channel; characterised in that the outer housing further comprises a second slider, oppositely disposed from the first slider, wherein the first slider is configured to slide toward a midline portion of the coupling element from a first direction, and wherein the second slider is configured to slide to the midline portion of the coupling element from a second direction.