For the Sony FX3, I would recommend using a CFexpress Type A memory card for the best performance. The FX3 has a CFexpress Type A/SD card slot that supports the newer and faster CFexpress standard. Some good options to consider:

• Sony CEA-G160T CFexpress Type A Memory Card
• Lexar CFexpress Type A Gold Series

These CFexpress Type A cards offer read speeds up to 800MB/s and write speeds up to 700MB/s. This will enable you to record high-quality 4K video at high frame rates with the FX3 without any buffering issues. The 160GB capacity is also ideal for longer recording times.

If you prefer to use SD cards, make sure to get a fast UHS-II card with V60 or V90 video speed rating to keep up with the high bitrates. Some good SD card options:

• Sony Tough SF-G UHS-II SD Card
• SanDisk Extreme PRO UHS-II SD Card

However, for the absolute best performance especially when recording 4K 120p video, CFexpress Type A is the way to go with the Sony FX3. 

For shooting video, I highly recommend a fast CFexpress Type A card. Any brand works OK.

I use Sony Tough CFexpress Type-A cards, works well on my FX3. Highly recommended !

I love Lexar gold series card: https://www.amazon.com/dp/B0B6QHHN9V/

So anyone uses SD cards on FX3 ? How are they performance ?