Review on Black USB Type-C to USB-A Male 3.1 Gen2 Adapter Charger Cable - 3ft (0.9m) - Amazon Basics by Tio Kotaki

Ideal for Retina MacBook. This cable is what you're looking for to use Target Drive Mode on your new 12" MacBook Retina. Holding down "T" while rebooting will put your MacBook into Target Drive mode and connect to another via USB Mac can be connected and mounted as a drive. On screen. It makes transferring files to/from MacBook very easy. Speeds are excellent, full speed USB-3. I've tried several cables with these connectors and this is ONE, which meets the standards and works great.It also allows the rMB to be charged with a standard 12W 2.4A USB charger.This charges very slowly but is great in a pinch, or if you're really packing a light have to.