Olympus 1.4X MC-14
(From company literature) Ideal for getting extra close to your subjects beyond your lens' capability. The MC-14's splashproof, dustproof and freezeproof all metal construction is compatible with the M.Zuiko ED 40-150mm f2.8 PRO and will also be compatible with the M.Zuiko ED 300mm f4.0 PRO (Available in 2015).
By placing this teleconverter between the camera body and lens, you can increase the magnification of your subject up to 0.6x (equiv. 35mm) and extend the focal length by a factor of 1.4x (40% more reach). When coupled with the M.Zuiko ED 40-150mm f2.8 PRO lens, a maximum focal length of 210mm (420mm equiv. 35mm) can be achieved. Macro shooting is possible at a working distance of 20 inches (50 cm).
When using a 1.4x teleconverter, you lose 1 stop of light, so for example, when using an f2.8 lens, the widest aperture you can use the lens at is f4.0.