This slide shows some typical tag form factors. On the upper left are shown the well-known ISO or clamshell cards, and below, several key fobs. Both are mainly used for access control systems. The image on the top shows a so-called E-unit which is typically packaged in a plastic housing and then attached to the ears of cows, sheep, goats and pigs. The upper right image shows glass transponders which are injected under the skin of the animal. E-units are also used in any kind of circular disc tags for general identification purposes. Microchip's complete tag solution, a transponder, is shown bottom right. This type of tag is commonly used in the automation industry.