OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
Apple: MacBook Pro 15'' Retina Mid-2015: Upgrade RAM to 32Gb - YouTube
Is there a way to upgrade the RAM in an early 2015 MacBook Pro without voiding the warranty? - Quora
Amazon.com: Mid 2015 Apple MacBook Pro with 2.5GHz Intel Core i7-4870HQ (15 inches, 16GB RAM, 512GB SSD) Silver (Renewed) : Electronics
macbook pro - Can I upgrade RAM on late 2013 retina Mac Book Pro? - Ask Different