The 2017 MacBook Pro Touch Bar SSD uses a proprietary connector

The 2017 MacBook Pro 13-inch Touch Bar is a mixed bag for storage upgrades. Some configurations have the SSD soldered to the board — good luck. Others use a proprietary Apple connector (not standard M.2), but you can technically replace them with a compatible third-party drive or an adapter-based M.2 NVMe. The interface is PCIe 3.0 x4 NVMe, so performance is solid when you do get it working — but the hoops you have to jump through are ridiculous for what should be a basic upgrade.