OWC Tears Down iMac Retina 4K, Confirms Memory Is Soldered
OWC 32GB (4 x 8GB) PC14900 DDR3 1866MHz SO-DIMMs Memory Compatible with 2015 (Late) iMac 27" w/Retina 5K Models and Compatible PCs (OWC1867DDR3S32S) at Amazon.com
OWC 8GB (2 x 4GB) PC12800 DDR3L 1600MHz SO-DIMMs Memory Compatible with 2011-2015 iMac, 2011-12 Mac Mini, and 2011-2012 MacBook Pro (Non-Retina Display) Models (OWC1600DDR3S08S) at Amazon.com
Apple iMac 5K Retina 27" Desktop - 3.2GHz Quad-Core i5 - 16GB RAM - 1T – The Refurbished Apple Store