OWC 64GB (2 x 32GB) PC21300 DDR4 2666MHz SO-DIMMs Memory Ram Module Compatible with Mac mini 2018, iMac 2019 and up, Dell, HP, Lenovo, ASUS and Compatible PCs (OWC2666DDR4S64P)

Easy to upgrade. Good performance increase with low cost.

I am pleased with OWC for offering great instructional videos and the tools needed to install, and also very pleased with this purchase through Amazon which made an exchange very hassle-free. First set of memory modules were installed properly but found to be defective, leading to successive macOS kernel panics/crashes on my device (I ran Apple diagnostics which did not detect anything abnormal). Amazon initially directed me to the OWC customer site for troubleshooting, but I went with a product exchange through Amazon instead and it was shipped next day. After swapping out the modules for a different set, all is working perfectly. Thank you Amazon and OWC.

Followed the video instructions for installing in a 2019 iMac 27”. It was a breeze and the new memory was recognized right away.

Excellent product Mac desktop 2019

Upgrading my 2019 27" iMac to 32GB of RAM was a fast and a painless effort. The entire process was less than 5 minutes. The computer booted right up and worked perfectly.

Mu purchase of 16 GB (2x8 GB sticks) of DDR 4 2666 ghz ram went smooth all of the way. It was delivered on time and very easy to install in my 2020 iMac 27". I figured I only needed 16 GB based on my Apple computer Activity Monitor assessment but decided I would try to add it to the existing 2x4 GB sticks I had.For the un-initiated: This computer uses 2 channels for ram. These both must be used or the effect will be decreased random access memory **availability**. There are 4 (four) slots for ram sticks. Channel A is slot 1 and 2, Channel B is slots 3 and 4. To work optimally, so I was led to understand by YouTube videos, the must carry the same amount. To illustrate, I now have 8 + 4 in Channel A and 8 + 4 in Channel B.If I had put this in any other configuration it would not work the same nor would it be optimal.In summary, I now have more than enough ram (there was no availability of 8 GB (2 x4 sticks). It was a bit more expensive than I had seen a year ago but that is life, I guess, you snooze you lose :^)

This RAM failed and the response for replacement has been slow as molasses with a thousand excuses, questions left unanswered, even after repeated requests for an urgent replacement, they still stall and take their time claiming they are efficient. They didn't have the replacement in stock with no date of restocking. Listen to the online reviews. If you are buying this RAM because you think it is the best, think again. If you are buying this RAM because you think their lifetime warranty will help you, think again. They will stall, write you an email every other day, no phone support for warranty, and when they fail in their customer service, they deny it. This is not a company with quality RAM. It was my first and last purchase. Going to buy Crucial RAM moving forward. What a waste of time and energy. Oh, when they do finally give you the solution in the replacement after weeks of agonizing ignorance of your emails and questions, they want you to feel oh so grateful that they are helping you. Like they are doing you a huge favor. Good riddens.

I've been an OWC customer for many years. I purchased this memory for a 2019 27" iMac (last with user-replaceable memory). After installation I had a number of random blue-screen reboots in my Bootcamp Windows environment and several random restarts in Mac OS. Support suggested I install the new memory 1 stick at a time, restart, repeat, to give the OS time to "learn" the new memory. I thought that was very odd. I didn't take that advice, but after a few days of being installed the memory issues just went away on their own (strange). Now after a month of daily use, they have been solid. I guess you just have to be patient?