Olympus Zuiko Digital 25mm 1:2.8 Pancake lens (Four-Thirds mount)

The Olympus Zuiko 25mm 1:2.8 is a very compact 'pancake' prime lens for Four Thirds DSLR cameras. When paired with one of the Olympus e-series cameras, it makes for perhaps the most portable true DSLR (with a real optical viewfinder) you can buy. 

Please note that this is a Four Thirds mount lens not the later Micro Four Thirds. Inexpensive adapters are available to allow these lenses to used with M4/3 bodies.