Looking to increase my iMac's RAM I am looking to increase the RAM of my iMac (Retina 5K, 27-inch, Mid 2015). I found one on the Apple website, but it is $400. If I could find a better price, it would be amazing. I was looking around on Amazon, but don't know if the SDRAMs I found work with my iMac. Do you guys have any advise for how to tell whether or not the SDRAM is compatible with my iMac?
The official RAM specifications are given by Apple here:
https://support.apple.com/en-us/HT201191

Using the list, you need to


  Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:
  
  
  PC3-12800
  Unbuffered
  Nonparity
  204-pin
  1600MHz DDR3 SDRAM
  


Note that only 32 GB of RAM is officially supported.