Maximize your performance with this internal 480 GB SSD drive. The form factor is M.2, which allows the hard drive to connect directly to the motherboard.
From Amazon
Transcend 480GB JetDrive 850 SSD (without enclosure) for MacBook Air 11" & 13" (Mid 2013 – 2017), MacBook Pro Retina 13" & 15" (Late 2013 – Mid 2015) Up to 1600/1400 MB/s TS480GJDM850
Conrad Electronic
Transcend JetDrive™ 850 Mac 480 GB NVMe/PCIe M.2 internal SSD M.2 NVMe PCIe 3.0 x4 Retail TS480GJDM850