It is working, I have researched trought some forums.
It is using the same ring (72mm) for FX1 and Z1 cameras.
And more: read below answer from LETUS SUPPORT TO ME:
Hello,
Yes. You can thread either the Extreme or soon to be released Ultimate to the end of the stock lens.
We are planning to develop a modular addon in the future that will allow you to attach the Letus adapter directly to the camera body.
Aaron
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www.letusdirect.com