Panasonic DMW-TC20E

I had previously said it works with Olympus. It does, but the image stabilization does not recognize the teleconverter. The 300 mm lens gets IS for 300 rather than 600 mm. It still works well, but you do need a higher shutter speed.

I finally received the lens and was able to use the teleconverter. All that it said it was and more!

It does fit the Olympus 300mm. The auto focus and exposure are working properly. I have not critically evaluated the picture quality, but have high hopes because lens and teleconverter seem to work quite well together. Olympus and Panasonic continue making compatible products that work well together.