Hi there
One of the recommended SD cards, as per O4 Pro specs, is Kingston Canvas Go Plus.
I bought three of these but none of them work on the air unit (they do work in my goggles N3).
No matter what video quality I set for recording, the air unit always throws “sd card error”.
Other SD cards I have work fine up to 4K 60 fps, but I haven’t managed to record at 100 or 120 fps yet as they are too slow. I guess I will have to try with more expensive sd cards?
Any thoughts on the Kingston Canvas?
Can you not format them in the Air Unit?
That normally sorts any compatibility issues
It throws error when I try
Have you a link
Yep
Bought it from amazon too
At just £6 quid from Aliexpress, it’s probably a fake card 
If you’re buying from Amazon and the seller is not Amazon direct, it’s also probably a fake
Try a SanDisk Extreme Pro:
Yeah, or one of those Pro ones 
I bought one.
Lets see how it goes
I can vouch for the sandisk extreme pro cards and the non pro both work great I’ve got them in all my tech. Usually pick up a few in the black friday deals every year as you can never have to many. 
I suspect they’re probably fine, but beware of a market flooded with cheap fakes 
The one I bought from amazon came from Kingston
I just bought a few of the amazon basics ones, they’re rapid. Copying off at over 100MB/s which was plenty for me pulling content off the o4 pro. Edit: just re-read you want 4k 100fps. Not tried it yet but think it should be fine.
The 4k60 h265 content was about 1GB/min so the 4k100 could be say 2GB/min meaning sustained write speeds of 30MB/s - should be easy for these cards, no?
I always now use Sandisk, never had a problem. Did try Kingson compact flash in my camera, tbh it was utterly crap, I tried another make (can,t remember which, but that had issues too. Lesson learnt- Stick To Sandisk, in almost 20 yrs of digital photography I’ve never had a single problem with Sandisk. Get the fastest you can to avoid buffering issues.
Ok there might be a possibility that I am actually recording at 120 fps with no issues, but I have issues when playing the video on my pc.
It stutters a lot, so I associated that to a “corrupted” recording due to a slow sd card, but maybe the reason is my pc struggling ???
Could someone kindly check the video I uploaded and tell me if there is something wrong with it?
Thanks
Ok it embeds the video which is not ideal.
I zipped the video and can be downloaded from here
Plays OK for me - and Davinci Resolve is happy to edit it. 
Ok It seems a pc problem then.
I imported the video in Capcut and exported at same resolution and frame rate.
The exported video plays fine.
odd
But you said
