There are several different types of patents. Most countries offer utility patent protection to protect the structure or function of an invention. About thirty-six countries offer utility models, which are similar to utility patents, but are usually less rigorously (if at all) examined and have a shorter term (typically ten years). Some countries offer patents of addition, to protect improvements to previously patented inventions. Still other countries offer design patent protection or patent-like protection for industrial designs. A handful of countries offer plant patent protection for plants. A few countries offer patents of importation or other patent protection based upon patents obtained in other countries.