Yes, the ProGrade Digital V60 128GB SD is compatible with the Sony FX3.
The ProGrade V60 is an SDXC V60 card. It meets the FX3's stated SD floor for XAVC S 4K (V60 or higher) but not the V90 required for XAVC S-I 4K, so it works for standard 4K only.
Limitation
Cannot record XAVC S-I 4K (intra-frame, up to 1200 Mbps in S&Q mode) -- requires Video Speed Class V90 per Sony's own spec, this card is V60. Works for XAVC HS/S 4K (V60 required, met) via the SD slot -- FX3's SD slot supports up to V60-tier 4K directly, no CFexpress required for standard modes.
“XAVC S 4K 280Mbps CFexpress Type A memory card (VPG200 or higher) SDXC V60 or higher”
“V60 Video Speed Class rating, which guarantees minimum write speeds of at least 60 MB/s”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)