Amazon.com: Dataram M.2 2280 256GB PCIe NVMe Gen 3.0 x4 SSD Compatible with Apple MacBook Air (2013-2017) & Pro (2013-2015), Mac Mini (2013) & Pro (2014), iMac (2013-2019) : Electronics
What is an M.2 SSD?
DATARAM 512GB M.2 M-Key PCIe NVMe SSD for 2013-16 MacBook, Mac Pro, Air, Mini, iMac - Newegg.com
M.2 SSD and Beyond: What is Ahead for the M.2 Slot?
Understanding M.2, the interface that will speed up your next SSD | Ars Technica