These new ND clip-in filters are now available at BHphoto, Amazon, Amazon DE, Amazon UK.
Kolarivision writes:
We’re excited to introduce our new Kolari Magnetic Clip-in Filters for Sony E-Mount! Compatible with most Sony mirrorless systems, our Kolari Magnetic Clip-In Filters can be used to add rear filtering to Sony E-mount full-frame cameras. They contain an anti-reflective, anti-smudge coating to make cleaning and maintenance easy.
Here are two Instagram videos showing how it works: