Crucial RAM 64GB Kit (2x32GB) DDR4 2666MHz CL19 Memory for Mac CT2K32G4S266M

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!

Got these to replace the RAM in my 2019 iMac (27inch). Did wonders for my computer's speed and overall functionality. Very easy to put in yourself, too, if your computer can do that.

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 upgraded my iMac RAM to 40gb total from the original 8gb purchased. Buying the additional RAM from somewhere other than Apple will save you a boat load of money. I researched that Crucial was one of the better brands to purchase and were compatible with Mac's.I did have the usual difficulty that other reviews are stating. I originally replace the original existing RAM (2x4gb) with this Crucial kit (2x16gb) and then placed the original RAM in the remaining open slots -- DID NOT WORK for me had black screen for longer than 2 minutes. I then switched the cards around to other positions, again it did not work. Finally, I placed the original RAM in their original slots and the NEW Crucial RAM into the remaining slots (slots 1&3), I made sure to be very careful and make sure everything seeded properly and firmly -- THIS WORKED! After about 20 seconds of the iMac configuring itself the Apple logo appeared.I don't know why the iMacs are very finicky to RAM but they are and from the looks of it, MOST people are having a bit of trouble with getting it initially installed. But after some moving around and making sure they are seeded in their slots properly, it WILL work, just be patient and don't get to stressed when the iMac doesn't boot after your first couple of try's.That said, I am pleased with the product and the expansion to 40gb's is overkill for me, but will make this machine a good "10 year" computer, and heck if need be I can still upgrade it to a full 64gb.Final conclusion -- Great product -- Place the new RAM in the open slots (1&3) -- Give the computer 30 seconds of black screen and it will boot up, otherwise check to make sure everything is seeded and inserted properly, my guess is that even the slightest offset throws the whole system off.

Compatible with my 2017 27in Retina iMac. The speed was immediately noticeable. My music software is handled and simple programs like the Finder and the internet don’t take forever to start up anymore. Also I can begin opening applications much sooner after the initial login. When I put the new cards in I took the old ones out and my iMac wouldn’t boot. I put the old ones back in with the new ones still inserted and it booted fine. It took a while to boot the first time but after the first boot every boot after was regular (I didn’t time it).