An inter-vertebral implant wherein at least one of the side walls defining a hole from the exterior of the implant to the fusion promotion cavity and having a posterior portion and an anterior portion, the side wall hole being elongated in a direction between the posterior and anterior ends of the side wall hole. In some embodiments, the side wall hole is tapered toward the posterior portion of the implant and can be tear drop shaped. In some embodiments the cephalad and caudal surfaces may be convex with radii of curvature which can be the same for all implant sizes. The surfaces may include teeth which can extend beyond a central cavity. A nose, tapered in the saggital and transverse planes may be included on the anterior end of the implant. Some embodiments also include a threaded hole (with a depth that can be the same for all implant sizes) and an adjoining slot for engaging an insertion instrument. Each of the portions of the implant can have the same length for all implant sizes.