A spinal fixation system may comprise a body, a tower, a set screw holder, and a set screw. A body may comprise a saddle, at least two tabs connected to and extending proximally from the saddle, a receiving channel disposed between the at least two tabs, and a securing mechanism, such as internal threads. A tower may comprise a central shaft configured to be received into the receiving channel, a cannula, at least two panels, an enlarged section, and an attachment feature configured to slide proximally and distally between the at least two panels and the enlarged section. A set screw holder may comprise a receiver and an insert. A receiver may comprise a passageway and a set screw engaging feature. The insert may be is sized to be received into the passageway of the receiver and may be configured to engage the set screw engaging feature.