SMD resistors are rectangular in shape. They have metallised areas at either end of the body of the SMD resistor and this enables them to make contact with the printed circuit board through the solder. The resistor itself consists of a ceramic substrate and onto this is deposited a metal oxide film. The thickness, and the length of the actual film determines the resistance. In view of the fact that the SMD resistors are manufactured using metal oxide, means that they are quite stable and usually have a good tolerance.