I bought a 2,5” SSD for my thinkpad e595 and when I've opened it, theres something in the ssd slot. I bought it just with M.2 memory, so I don't know what
Lenovo ThinkPad T420s Hard Disk Drive Replacement - iFixit Repair Guide
Finally added mSATA SSD to my T420 and now have 3 drives booting multiple operating systems, what a joy 😁 : r/thinkpad
ThinkPad T420 Hard Drive Replacement - iFixit Repair Guide
Amazon.com: Lenovo Thinkpad T420 - Intel Core i5 2520M 8GB 320GB Windows 10 Professional (Renewed) : Electronics
Amazon.com: CMS 128GB mSATA 6GB/s Internal SSD Compatible with Lenovo ThinkPad T420 Series - C29 : Electronics