A pedicle screw implant construct kit, comprising at least one pedicle screw, at least one collar comprising a recess for receiving a rod, the collar configured to be coupled to a head of the pedicle screw, an elongated rod for connecting the collar to one more additional collars to couple between the pedicle screw and one or more additional screws, and a locking ring sized to be positioned over at least a distal portion of the collar to restrain relative movement of the screw head and rod by exerting radial compression force onto the collar. In some embodiments, the components of the kit are comprised of carbon reinforced composite material, optionally with no radiation blocking material. In some exemplary embodiments of the invention, the kit includes two locking rings on a collar, optionally both below the rod.