There is a long-standing interest in use efficiency and evolution in prehistoric ground stone tool research. A design and performance analysis conducted with replica tools examines a number of milling tool performance characteristics, including use efficiency, ease of manufacture, and ease of maintenance, as well as their interplay in the design process. This analysis shows that raw material and use surface area affect use efficiency. A paradigmatic artefact classification documents the variation in prehistoric manos from archaeological sites in the Middle Rio Puerco Valley of New Mexico. Contents: Introduction; Background and research; Hypothesis; Methods and procedures; Results; Discussion; Conclusions.