SanDisk SDSDXN-128G-G46 Extreme 128GB SDXC Card UHS-I U3 — main product image

SanDisk SDSDXN-128G-G46 Extreme 128GB SDXC Card UHS-I U3

SanDisk

SanDisk SDSDXN-128G-G46 Extreme 128GB SDXC Card UHS-I U3

Name: SanDisk SDSDXN-128G-G46 Extreme 128GB SDXC Card UHS-I U3
Brand: SanDisk
SKU: SDSDXN-128G-G46

★★★★★4.6 (3644 reviews)

4KUHD1080p

U3-rated 60MB/s writes and UHS-I bus performance keep the SanDisk Extreme 128GB ahead of the buffer on continuous 4K UHD capture.

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Overview

The SanDisk Extreme SDSDXN-128G-G46 is a 128GB SDXC card operating on the UHS-I bus with a Speed Class 3 (U3) and Video Speed Class 30 (V30) rating, specifying a minimum sustained write of 30MB/s. SanDisk's rated performance for this card exceeds that floor at 60MB/s write and 80MB/s read — figures that place it at the practical performance ceiling for UHS-I SDXC media. The UHS-I bus itself has a theoretical maximum of 104MB/s, meaning this card operates at roughly 77% of the bus ceiling on reads, leaving minimal slack. For 4K UHD recording at standard consumer bitrates of 60–100Mbps (7.5–12.5MB/s), the 60MB/s write spec provides approximately 5x the headroom required — a buffer that absorbs encoding spikes and protects against dropped frames under normal recording conditions.

This card is sized and rated for DSLR and mirrorless photographers who shoot extended sessions in RAW burst mode and videographers capturing 4K UHD content without card changes. At 128GB, it holds a full day of mixed stills and video for most field shooters. The 80MB/s read spec translates directly to post-production speed: offloading a full 128GB card over a UHS-I reader completes in under 30 minutes, a tangible reduction in turnaround time for event and wedding workflows. Buyers with cameras featuring UHS-II slots should note that this card will function correctly but will not saturate the slot's higher bandwidth — a UHS-II card would be the appropriate specification match in that case. For UHS-I equipped bodies, this card hits the practical performance ceiling of the interface.

Key Features

Performance/speed: Up to 80MB/s read & 60MB/s write

Ideal for advanced cameras, DSLRs and HD camcorders

Seamless 4K UHD and Full HD(1080p)video

Durable and reliable

Specifications

Capacity

128GB

Form Factor

Full-size SDXC

Bus Interface

UHS-I

Speed Class

U3 (V30)

Read Speed

Up to 80MB/s

Write Speed

Up to 60MB/s

Video Compatibility

4K UHD, Full HD (1080p)

Pros & Cons

👍 Pros

80MB/s read speed enables fast post-shoot offloads — approximately 1.6GB/sec sustained across a UHS-I card reader connection, cutting transfer time meaningfully versus mid-tier alternatives.
60MB/s write rating is double the U3 minimum floor of 30MB/s, providing buffer overhead during high-bitrate continuous recording rather than operating at the speed class's margin.
128GB capacity holds multiple hours of 4K UHD footage at consumer bitrates, reducing mid-shoot card swaps for most field and event recording scenarios.
SDXC format is natively supported in modern DSLRs, mirrorless cameras, and HD camcorders without firmware updates or adapters.
SanDisk's established UHS-I controller maturity means real-world sequential throughput consistently tracks close to rated specifications under sustained write load.

👎 Cons

UHS-I bus caps theoretical maximum at 104MB/s — cameras and devices equipped with UHS-II slots cannot use this card's slot to its full potential, as a UHS-II card in the same slot would achieve significantly higher throughput.
60MB/s write is specified as a maximum, not a guaranteed sustained floor — write speed can dip under small-file or random-write patterns, which affect burst shooting in RAW more than it does video recording.
Full-size SD form factor is incompatible with devices using microSD slots without a separate adapter, adding a component failure point in mobile or drone workflows.
Not suited for professional raw video formats such as CinemaDNG or ProRes RAW recorded to SD — those bitrates typically demand UHS-II or CFexpress media.

Frequently Asked Questions

What does UHS-I U3 mean, and why does it matter for video recording?

UHS-I defines the card's bus interface — a theoretical maximum of 104MB/s over the SD slot. U3 is the minimum sustained write speed class at 30MB/s, but this card achieves a specified 60MB/s write — double the U3 floor. That sustained write headroom is what prevents dropped frames during continuous 4K UHD recording, where the data stream consistently demands above 30MB/s.

Will this card work in cameras and devices that use older SD standards like UHS-II slots?

Yes, but only at UHS-I speeds. UHS-I and UHS-II are backwards compatible — this card will function in UHS-II slots, but will not benefit from the faster UHS-II bus. Conversely, placing this card in a UHS-I slot is its native environment and will achieve its rated speeds.

Is 128GB enough capacity for 4K UHD video production?

At typical 4K UHD bitrates of 60–100Mbps for consumer cameras, 128GB holds approximately 2–3 hours of continuous 4K footage. For DSLRs shooting in compressed formats, capacity is higher. For professional raw or high-bitrate cinema formats, 128GB fills faster and may require multiple cards per session.

What does the 80MB/s read speed mean for offload and workflow?

At 80MB/s sequential read, transferring 128GB of footage to a workstation over a fast UHS-I card reader takes roughly 27 minutes. This is a meaningful improvement over budget cards that read at 20–30MB/s, which would require over an hour for the same transfer — a practical difference for production workflows on tight turnarounds.

Is this card compatible with smartphones or tablets that have a microSD slot?

No. This is a full-size SDXC card. It is not compatible with microSD slots. An SD-to-microSD adapter is required for devices that use the smaller form factor.