Yes, the Canon EOS R5 Mark II is compatible with the SanDisk Extreme microSDXC UHS-I 128GB.
Canon EOS R5 Mark II has a full-size SD card slot. SanDisk Extreme microSDXC UHS-I 128GB (real write speed 130 MB/s) fits via the bundled microSD-to-SD adapter and clears every recording mode including this camera's top-tier mode requiring Video Speed Class 90 (90 MB/s).
Limitation
Cannot record 4K60 (Video Speed Class V60), 4K120 (V90), or any CFexpress-only Intra/RAW mode -- Canon's own manual lists no SD card alternative for these modes, this card is V30. The bundled microSD adapter provides physical fit only; it does not change the card's class rating. Works for 4K-UHD Fine Standard LGOP (29.97/25/24/23.98fps) via the SD slot.
“CFexpress cards Type-B compatible SD/SDHC/SDXC memory cards UHS-II and UHS-I cards compatible Cards That Can Record Movies When recording movies, use a CFexpress card that supports VPG400 or a card wi”
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