An improved back reamer for horizontal directional drilling is provided with multiple components which can be assembled and disassembled before and after the back reaming process. The reamer includes a main shaft connectable to the drill string, a reamer head removably mounted on the main shaft, and a pull tab removably attached to the main shaft. Faceted couplings between the reamer shaft and head, and between the reamer head and pull tab preclude rotation between the components.