Crucial CT2K16G4S266M 32GB (16GB x2) Mac Memory Kit (DDR4, 2666 MT/s, PC4-21300, CL19, Dual Rank x8, SODIMM, 260-Pins)

I purchased memory from OWC for my 2020 iMac 27" twice, and each time the memory did not work. One set wouldn't allow my computer to turn on at all, and the next set caused my computer to reboot about 5 mins over and over. I was very frustrated, and decided to give the Crucial memory before giving up on upgrading. It installed in ~3 mins and has worked flawlessly with no reboots, no crashes, no issues at all. The iMac has never run better, and I'm relieved to have found a solid solution for a good price.

I was a bit concerned prior to installing my 32 GB kit - the reviews I read here, made it seem like I would encounter issues with slot placement and seating the cards. I'm a mom of two and I'm moderately tech-savvy (I've installed an SSD drive in my previous iMac without issue), but I'm in no way an Apple Genius. The entire process actually took me about 15 minutes (to be honest, 10 minutes of that was just unplugging everything and setting-up a clear/soft workspace on which to set the computer). After popping the cover off the back of the machine, I didn't change the position of the original RAM cards- I just added the two new 16 GB cards to the remaining/available slots- I didn't have a problem seating the cards at all. Then I replaced the cover, plugs and powered my machine on- there was an initialization prior to my log-in screen that was a tad bit longer than usual, but once I signed in, everything seemed in order- "About this Mac" reflected that I had 40 GB of RAM and the application I use to monitor my RAM usage had shown an impressive increase. Prior to installing this RAM- my available RAM would hover around a paltry 25 MB (I use Adobe applications, like Photoshop, Lightroom, Illustrator and InDesign regularly), but after installing the upgraded RAM- I'm showing at least 30 GB of available RAM. For the price and ease of installation- I can't give a better endorsement. If you're on the fence about buying it, I can honestly say I'm extremely happy with this product!

9-4-25. I've had these for only a couple of days and have no problems. My Photoshop and Lightroom Classic programs have gotten so big that they were crashing my 2020 imac. The 8 gigs it came with couldn't handle the programs anymore. I installed these 2-16 gig cards along with the 2-4 gig cards that came with the system. I left the original 4 gig cards in slots 1 and 3 and put these in 2 and 4 as recommended by the interweb. The machine fired right up and I've had no issues so far with the programs. From 8 gigs to 40. If anything goes sideways I'll update this review.

As always, Crucial is the best all around brand for Apple's (upgradable) computers. Crucial is owned by Micron, a company that Apple themselves uses as an OEM supplier. If you've ever pulled RAM out of a Mac before, you might have seen "Micron" on the labels. Crucial supplies their own branded components that you'd never see inside as OEM on a Mac, but the RAM itself is Micron underneath the Crucial label. It's the brand I always trust most with RAM upgrades on a Mac. It's not the cheapest, and is far from the most expensive. But it is the most dependable. And trust me, you want dependability if you're going to go through the hassle of upgrading the memory on a 2019 iMac. That said, installing RAM on a 2019 21.5" iMac is no easy task, at least not for the faint of heart. You'll also need to order yourself new display adhesive as you cannot reuse what was on the machine. I'd also advise that if you're going to go in, to also upgrade anything else that needs upgrading (SSD, adding a second drive, CPU, etc). Because it's not easy or fun in there, it's just nice to knock it all out of the park if you can. Also make sure you have your Torx screwdrivers ready as you'll need T5, T6, T8, T9 and T10 sizes, in addition to a P00/P000 screwdriver. Make sure the screwdrivers come magnetized, and if not get yourself a driver magnetizer/demagnetizer. It's quite the journey in there, which you should look into over at ifixit.com before you order a single thing.

I have an iMac Pro (2017, retina, 27", base memory 8GB) that I like except for the memory - it's too slow, and gets jammed up if I've opened too many programs. With great trepidation, I read the Apple specs to see what memory I should get to upgrade, found that the local shops didn't have much on hand, and decided to do it myself. The directions seemed straightforward, but this isn't my strong suit, and my hands aren't particularly strong, so I didn't know if I could remove the original memory or seat the new memory. I ordered a set of two 16GB memory chips for this model, and waited until someone was around in case something went awry who might be able to assist. Apple's explanation was very clear about how to add memory. I also read reviewer comments to see what problems others had encountered. The only hitch was in pushing the button to open the memory compartment - that needed more pressure from an implement other than my finger (e.g., a small screwdriver). I decided to try using the two empty slots, leaving the old 4GB chips in place, since it would still be balanced, and put the chips in (easily), closed up, put the cables back and the machine upright, and voila! It worked! my iMac is much quicker, and so far it hasn't frozen or "jammed up", so I'm very pleased with these chips. They have made a noticeable, welcome change, and I'm not feeling like such a klutz!

UPDATE TO ORIGINAL REVIEW: After installing the second set of sticks, which replaced the first two defective ones I received, everything now works great. Now have both the original Apple sticks (2x8) functioning perfectly with the new Crucial memory (2x16) for a total of 48G - with no issues, so revised original review accordingly. -------------- Original Review Below ----------------- Having installed Crucial RAM in at least two other iMacs in the past with no issues, and after reading reviews by other satisfied buyers who had the same model Mac (2017 4.2ghz, i7 2TB), I was not expecting to experience any performance problems. I bought the mint-condition Mac off eBay, and decided to add some extra memory to the original 16g of RAM to allow for more headroom for use with a DAW, as the activity monitor consistently showed about 14 gigs being used with just a few programs open. However, soon after installing, the Mac started acting strangely… Whereas the computer was completely mouse-silent before adding the new RAM, after installation, the fan would randomly kick on and the Mac would seem to be gasping for breath even during non-memory intensive operations. At first it didn’t occur to me that the new modules could be the issue, but after calling Apple and executing some basic troubleshooting, I decided to remove it - and sure enough, the Mac was completely silent again - even with several apps open during export operations. It was conclusive - there was definitely a conflict with this particular RAM. So called Crucial directly to get their opinion, and they suggested that mostly likely the memory was bad, and advised returning and replacing. So planning to do just that, or try a different brand like Kingston… p.s. In the photo, the label on the plastic container said “Notebook” which initially made me think that I was sent the wrong memory for this Mac, but the Crucial rep said it didn’t matter, and should also work for my system. UPDATE: Received the replacement RAM, which I first installed along with the original 16g (2x8) Apple memory, and the result was an unresponsive, dormant black screen. After trying each possible configuration of installing the RAM with no success, I finally decided to remove the Apple memory and just leave in the new Crucial pair of 2 16g sticks - and now everything runs as silent and smoothly as I was expecting. So for now, must conclude that these two particular Crucial modules don't "play nicely" with the original Apple ones (have read a few other buyers making similar conclusions). Not the best outcome, but still an improvement in function overall, so considering adding another matching pair of 16 and will see how that goes.

These were excellent modules, and way lower than Apple's price for memory. Sad to see that Crucial (Micron) is no longer going to be in the consumer market. I used to live just down the road from the main facility in Boise. At least they will still be available from remarketers.

I have an Intel Mac that was struggling with 16GB of RAM. Looked into buying a Apple silicone mac mini but could not justify the cost of one that supported 3 monitors. Installation is simple with the right bit and now the Mac Mini is alive. There are some weird issues with Chrome and Bluetooth but only does it (shutters) maybe once a month and a restart corrects it.