Small Outline Diode (SOD) is a designation for a group of semiconductor packages for surface mounteddiodes. The standard includes multiple variants such as SOD-123, SOD-323, SOD-523 and SOD-923.[1] SOD-123 is the largest, SOD-923 is the smallest.
It is relatively common to find packages that contain other components than their designated ones, such as diodes or voltage regulators in transistor packages, etc.