We developed a highly efficient open source coordinate prediction method based on a fragment library. The new implementation improves both speed and stereochemical accuracy over the previous rules-based Open Babel implementation. We find that remaining issues often result from missing fragments, resulting in extended ringclosure bonds and in incorrect dihedral angles. Adding explicit rules to handle rare ring fragments and macrocycles will improve these issues. In some cases, molecules with large RMSD to experimental geometries reflect a difference between the lowenergy conformer generated by this implementation and the experimental pose, a known problem .