SanDisk 400GB Ultra MicroSDXC UHS-I Memory Card with Adapter - 100MB/s, C10, U1, Full HD, A1, Micro SD Card - SDSQUAR-400G-GN6MA

This card has not disappointed me yet. With huge amounts of space, and a transfer read speed listed at 100MB/s, it's a card that can serve all kinds of purposes—assuming your device supports this storage amount—for photos, music, videos, and just plain old file storage. I am using mine with the new Sony NW-A45/L Walkman with Hi-Res Audio, Moonlit Blue (2018 Model) , and it has worked marvelously so far, with all the memory being "seen" by the player, and some very good transfer speeds. I have not yet specifically tested the actual speed, but will do so soon with the Black Magic speed tester, and will update this review with that report. Right now (mid-2018) this card is running at just under $200. I don't suspect it will drop anytime soon, since its the only guy on the block, so if you have a use for it, you might as well get it now. I doubt this will even be marked down much towards the end of the year, although I could be wrong, due to its unique status. Having said that, if the price is still too high, keep an eye on it, because there MAY be occasional rebates, two-day sales, etc. It has all the standard SanDisk hallmarks: high quality, nice look, good performance, nice looks, and it, of course, comes with an adapter in case you wish to use this in a camera that takes the standard sized SDXC cards. I can put almost my entire lossless audio library on this one card, which is amazing. Five stars, and an update soon with the results of the speed test I plan to perform.

Bought this for my Paralenz underwater camera that shoots up to 4K 30fps. My camera manufacturer says 128gb V30 is the required max but this card is rated for a min of 10mb/sec & and the write speed is undocumented publicly after contacting Sandisk, with transfer speeds to 100mb/sec. Maybe they won't release write speeds because it performs so well they don't want it competing with their faster rated cards?.... just speculation of course! But this card performs flawless... not only in my Galaxy Note 4 phone but also in my camera. Leave it formatted in the default exFat and your good! After much research it appears its only weakness may be in burst abilities for use as internal memory but sustained transfer rates are great!... so much so that 4k @ 30fps video was no problem in testing. I'm also astonished this card works so well in my Note 4, I had a 128gb Sandisk in before and this definitely feels faster. At this point I have the highest recommendations for this card.... you can now store mass amounts of 4K footage.... according to my tests so far, about 10+ Hrs of 4K @ 30 fps! I've found other brands often give similar speeds as compared to Sandisk but fail miserably long term in reliability.... Do you really want 400 GB worth of stuff lost because you wanted to save a few bucks with another brand? Sandisk is the most reliable IMO and it's amazing they remain at the front of the pack. It's not the fastest dog out of the gate that wins, but the one who can make it to the finish line first! I own 3 of these now. I can film 2.7k @ 60fps and put 17 one hour dives in a week long dive vacation and I only use about 180gig! Its great not having to tote a big laptop on my trips! I have one just for backup too on my trips .. Haven't had to use it yet!

Not much to say other than to remark on the validity of the SD card I received through Amazon actually being from SanDisk. SanDisk is one of, if not the biggest, SD card manufacturer and the quality of their products is the golden standard. So capacity, performance, and reliability goes without saying for these SD cards. However, I have read quite a lot of reviews claiming that the ones they received were imposters and, while I do not claim they are mistaken or not, I can say that my 400GB one I received from Amazon seems to check out through every test I've run it through. Amazon has quality customer care and product replacement/return policies for the ginormous corporation they are, so if you have any issues with your product I'm sure you can get it worked out within reason. There are a lot of different resources for checking the validity of SD cards online and you can find them all with a simple search on a quality search engine website. If you are concerned, I suggest going that route or contacting local IT support to see what they can do for you. PROS: SanDisk. Enough said. Quality and performance. CONS: Obviously, verrry slim chance of the SD card being a fake. Technology is amazing these days and there are people out there driven to make a quick buck if they've got the materials and the know-how. Even giants like Amazon can fall victim to these numerous and unethical kinds of practices. Happy with my purchase. 100% 400GB SanDisk SD card at a reasonable price.

For dashcams and other continuous loop recordings: Sandisk markets a "high endurance" 256gb card @ $52, but it is a terrible deal compared to this 400gb SanDisk Ultra. The main selling point of a high endurance card is 1) it can take additional writes. This card can too since it also has storage space above 256gb, except unlike the 256gb card you can access the additional storage space from the get go, which is hugely important to increase the look-back period of your dashcam. 256gb is the current max storage for high endurance cards, if you want more storage you either have to periodically back up data to a hard drive or... you could just get the 400gb Ultra. 2) Some durability features. SD cards have zero moving parts, any condition that would destroy the Ultra would likely destroy the equipment containing it. There is only a narrow survivability delta, if any, where the high endurance would survive conditions that the ultra doesn't. 3) Warranty. The high endurance only offers 2 years warranty compared to 10 years on the ultra, but in the warranty terms the Ultra does not cover failures due to use in applications like dash cams. This is BS as all SD cards are already warranty-limited by write cycles. Write cycles are write cycles, regardless of whether they occur in a dash cam or a normal camera. Nevertheless this warranty is unnecessary as a) failures of legit microsds are extremely rare even in "high endurance" scenarios, and b) the costs of cashing in the warranty likely exceed the value of the replacement In terms of compatibility, many pieces of equipment will claim to have a limit of say 128gb but take this card just fine. In terms of write speed, a peak of 100MegaBytes/s is plenty for most consumer grade cameras. I've used it in an action camera and it can take sustained 4K 170 Megabits/s video (170 megabits = 20 MegaBytes) no problem. TLDR/Bottom line: If you can afford it and if you plan on using the card in a scenario where you might possibly, at some point need maximum storage, this is the option that provides the best value.

I love it! Works great in my Galaxy Note 8! Fast enough that I can throw pretty much anything at it. If you're wondering, modern Android versions (starting with Lollipop, as I recall) have the ability to read up to 1 TB of external storage. While this 400GB card is the maximum capacity you can currently buy*, the leading manufacturers are feverishly working to make larger capacity cards. For now, though, I think 400GB is enough to handle all the 4K video I can shoot. *- Don't be fooled by unscrupulous sellers, particularly on auction sites ( I won't name it because there are a lot of fake cards here, too), who list ridiculously large capacity cards for astonishingly low prices... you don't get what you pay for! They take cheap, generic cards, usually no more than 4 or 8 GB, and rewrite the card's firmware & re-label it to make it act and appear like a larger card... 256GB, 500GB or higher! There are tons of listings out there for 1 TERABYTE microSD cards! Of course there's no such thing: and when the physical memory of the card is reached, your device will simply start overwriting data... and your precious photos, videos and other files will be gone forever. In fact, one third of all SanDisk cards on the market are counterfeit! You can avoid all this by installing and using a free app called SD Insight to determine if your card is legitimate.

My review is based on using this microSD card to add extra memory for videos and photos to a Win10 Acer ZenBook that has 512GB SS memory. Adding 366 GB extra storage for this laptop’s microSD slot is much less expensive, and slower, than doubling the solid state memory. All the performance claims on the packaging and on amazon.com use a non-standard definition of a GigaByte (GB) and a MegaByte (MB). Using standard terminology, the capacity claimed is about 372GB, with a note that “actual user storage is less.” I found the capacity was 366GB, according the Windows. The claimed maximum read speed, in normal terminology, is about 95MB/s. I copied a couple large files from this microSD card to the Acer’s fast SS-memory, and Windows measured the read rate at just under 40 MB/s. I’d have expected such a copy to measure closer to SanDisk’s claims, so I knocked my review down to 4 stars. The game playing with GB and MB definitions is a bit silly too. I am very happy with the cost of adding this much extra storage to my laptop, and for storing large media like videos this seems like a great way to save on buying lots of more expensive solid state memory in a laptop. The microSD card was plug-&-play with no formatting required. If you want to understand the GB/MB numbers gimmick SanDisk uses, here’s the explanation. In normal computer terminology capacity numbers are tied to a base-2 system. A kilobyte means 1024 bytes, and a megabyte means (1024)(1024)=1,048,576 bytes. A gigabyte is (1024)(1024)(1024)=1,073,741,824 bytes. Sandisk defines a MB as 1,000,000 bytes and a GB as 1,000,000,000 bytes. This inflates their numbers. 400GB claimed, times 1,000,000,000/1,073,741,824 to convert to standard terminology, equals 372GB. 100MB/s claimed, times 1,000,000/1,048,576 to convert to standard terminology, equals 95.37MB/s.

I picked up the 400 GB version during Prime Deals for my Switch. Knowing that Nintendo is a little weird about storage formats, I searched its website to see what Nintendo recommended when replacing SD cards for the Switch. As it turns out, Nintendo very sternly recommends fully formatting SD cards with a special tool before using them in a Switch. "Nintendo recommends using the SD Association's SD Memory Card Formatter to format any SD cards that will be used with a Nintendo product. Nintendo products strictly adhere to the SD card standard. Instructions on using this tool can be found at the bottom of the tool's page on the SD Association website. Please select Overwrite format when formatting the card." The SD Association's site provides "It is strongly recommended to use the SD Memory Card Formatter to format SD/SDHC/SDXC Cards rather than using formatting tools provided with individual operating systems. In general, formatting tools provided with operating systems can format various storage media including SD/SDHC/SDXC Cards, but it may not be optimized for SD/SDHC/SDXC Cards and it may result in lower performance. SD/SDHC/SDXC Cards have a ‘Protected Area’ for SD Card security purposes. The SD Memory Card Formatter does not format the protected area in the SD/SDHC/SDXC Cards. The protected area shall be formatted by an appropriate PC application or SD host devices that provide SD security function.” In other words, unless you format your SD card with the tool from the SD Association's site, the secure sectors of the card get lumped in with the rest of the storage, slowing down the card. A quick format in Windows won't cut it here. I'm willing to bet this has caused the vast majority of one-star reviews complaining of poor SD card performance on Switch. I followed Nintendo's directions for formatting and the card performs perfectly. It seems a bit faster than my old card. A nagging data corruption issue I had with my BoTW install has stopped completely.

Summary: the SanDisk Ultra 400GB seamlessly adds what amounts to unlimited storage for your phone. I've had it installed and working well on a Samsung Note 9 for the last three months. After putting the SanDisk Ultra 400GB in place on my Samsung Note 9 , I don't think I'll ever run out of space on my phone. I love this: I never really have to download pictures or video from my phone, and I can permanently store whatever movies, documents, or other files I wish. Even after shooting thousands of photos and hours of video, I have hundreds of gigabytes of free space left. On the Samsung Note 9, the 400GB card reports 366.8 GB of free space after formatting. Using a speed testing application, my card reports write speeds of 48 MB/s and read speeds of 86 MB/s. Suggestions: * After purchase, get an SD card speed testing application to verify that your card isn't fake, and that its performance approaches SanDisk's hyped theoretical maximum. Don't be put off if you don't reach 100 MB/s or whatever the advertised maximum speed might be; you just want to be somewhere in the ballpark. If you are using Android, you can download an excellent SD cart-testing application from the Play store called "SD Card Test." * On some Android devices you can further verify that you have a legitimate (not fake) card by downloading an application called SD Insight (note this app is not compatible with the Galaxy Note 9 and some other late-model Android devices.) note: I was *not* solicited to write this review, and I bought this product with my own money. I received no compensation for this review and indeed I have no idea who the seller might be. I pride myself on writing unbiased reviews.