Low- and high-frequency tags work better on products with water and metal. In fact, there are applications in which low-frequency RFID tags are embedded in metal auto parts to track them. Radio waves bounce off metal and are absorbed by water at ultrahigh frequencies. That makes tracking metal products, or those with high water content, with passive UHF tags challenging. However, in recent years, companies have developed special UHF tags designed to overcome these challenges. There are also ways to tag products with metal or water content to ensure reliable read rates (members, see How to Tag Problem Products.)
