A precisely size matched intervertebral plate and spacer assembly for ensuring a tight fit within a disc space to promote spinal fusion, comprising: a “U-shaped” spacer configured to fit within the intervertebral space; and, a matching countersunk low profile “H-shaped” anterior plate joined perpendicularly to the spacer. The plate further comprises: a plurality of anchor members configured to attach to the junctions of the anterior cortex faces and the endplates; and, channels individually traversing through the anchor members for inserting screws into the vertebral bodies' cortical bone. The spacer comprises a hollow three-sided U-shaped member, comprising two opposing parallel side walls, and a perpendicular posterior wall, while lacking a superior, inferior, and anterior wall. The exterior walls of the plate and spacer are planar, while the interior walls of the spacer are curved to house a precisely fitting cylindrical graft, or other insert such as DBM, bone dust, bone paste, bone dowel with direct contact to the endplates to promote fusion.