3.2. Physical Characteristics

Because RFID tags must physically attach data to items of different shapes and sizes in different environments, they come in a wide assortment of shapes and sizes. Furthermore, they may be housed in many different kinds of materials. Some of the physical characteristics of various tags include:

• PVC or plastic buttons and disks, usually including a central hole for fasteners. These tags are durable and reusable.

• RFID tags shaped like credit cards, which are called "contactless smart cards ."

• Tags made into the layers of paper in a label, called "smart labels ." These may be applied with automated applicators similar to those used for bar code labels.

• Small tags embedded in common objects such as clothing, watches, and bracelets. These small tags may also come in the form of keys and key chains.

• Tags in glass capsules, which can survive even in corrosive environments or in liquids.