Solid and heavy as a little rock - top optics - no protection case included.
Heavy duty construction.
Top performance optics.
When unpacking the first thing I noticed : Small and Heavy.
In use:
Extremely precise fit bayonet - the protruding optic that goes into the lens is rubber coated to avoid lens damage.
Optical performance: I'd say 98% as good as my XF 100-400 Pro - some times a tiny bit of chromatic aberrations - too easy to remove in post process.
But dear Fuji:
Why not include a sold protection case for that money ? As it is a premium price to pay - almost 30% more as the Olympus equivalent.
Photo: An Australian Monitor Lizzard / Goanna in my garden. XF 100400 Pro + 1.4 tele converter. Processed in capture 1 - moderate sharpening.