Depending on the model and its corresponding purpose, droids were totally obedient, rugged, expendable, capable of vast memory recall, and mathematically precise. These characteristics made them well suited for many jobs, though the lack of independent thought in the cheaper, less advanced models limited their capability. This lack of autonomy was simultaneously a vast asset and a glaring weakness—an asset in terms of obedience and control but a massive drawback in terms of effectiveness. Designers faced a fundamental paradox—make the droids overly intelligent, and they might rebel; yet make the droids not intelligent enough and they would be ineffectual.