Dell Alienware X51 R3 AX51R3-6510BLK Desktop PC with Intel Core i5-6400 Processor, 8GB Memory, 1TB Hard Drive and Windows 10 Home (Monitor Not Included) - Walmart.com
▻ Alienware X51: How to upgrade your PC RAM (Gaming PC Tutorial/ Guide) - YouTube
16GB (2x8GB) Memory RAM Compatible with Alienware x51 R3 by CMS (B107) | eBay