While I have not purchased the modules from Amazon, but used a well-known auction house) - but that does not matter in my experience with the product.
The RAMs can operate together with the original installed by Apple Elpida RAM. I have tried them in two RAM banks - No problems (see photos).
It works its way noticeably smoother and faster than with 24 GB "only" 8GB :) This combination has now run for more than 1 year is very satisfactory, no defaults and impairments.
From then forth for me 5 star and a strong buy recommendation!
An important note yet:
It can be in the new iMac's (the narrow side) only upgrade the 27 "model.
The new 21 "models of RAM is permanently installed, so that you have to be on the purchase on the RAM expansion stage clear already!
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If you enjoyed or helped this review, I would be happy about an assessment very. In this way, to know whether the effort was helpful the reviewer.
Thank you for reading!