If you want fully crosspolarized shots for photgrammetry, photometry of even just for photography to block out all reflections of your ringflash and get correct color date, this polarizing filter is the best choice for your scanning device.
It's a pecise and smooth 3D printed frame together with a high quality linear polarizing film.
It's attachable through magnets directly to the ringflash and stays stable in every situation. Thanks to its magnets and the handle it is adjustable in 45 degrees to easily change from cross-polarized to parallel-polarized within seconds. It stays cool even on long scanning trips because of it's ventilation holes on the side.
It's compatible for the Godox Wistro AR 400, Quadralite RX400, Flashpoint RF-400 and RIKO400.
If you buy 9 you'll get one for free (Buy 9 get 10)