X1 Extreme Expansion Opportunities - No Soldered RAM in this X1 - Every single X1 Extreme will accept 4TB NVMe + 64GB DDR4 RAM whenever you are ready regardless of what it
CMS 64GB (2x32GB) DDR4 21300 2666MHZ NON ECC SODIMM Memory Ram Upgrade Compatible with Lenovo® ThinkPad X1 Extreme Non ecc - D48 - Walmart.com
How to upgrade the RAM and SSD on the Lenovo ThinkPad X1 Extreme