Abstract: A fastener and a bone fixation assembly for the internal fixation of vertebral bodies such as a pedicle screw is provided which allows a detachable tulip to be provisionally locked to a pedicle screw, while separately, the rod securely locks to the tulip. According to one exemplary embodiment, the tulip assembly includes a tulip body and an inner tulip member, the tulip body having a non-circular surface disposed on an outer surface. Additionally, a fastener is coupled to the tulip assembly and positionable to retain the tulip assembly on the head of a screw. Further, a cap having an outer surface and a plurality of inner protrusions is provided, wherein the plurality of inner protrusions are configured to mateably connect to the non-circular surface on the tulip body to compress the tulip assembly and secure a rod.