The Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter lets you connect Thunderbolt and Thunderbolt 2 devices - external hard drives and Thunderbolt displays, for example - to any of the Thunderbolt 3 (USB-C) ports on your MacBook Pro. As a bidirectional adapter, it can also connect new Thunderbolt 3 devices to a Mac with a Thunderbolt or Thunderbolt 2 port. Compatibility- 13-inch MacBook Air with Retina display, 13-inch MacBook Pro - Thunderbolt 3 (USB-C), 15-inch MacBook Pro - Thunderbolt 3 (USB-C), 21.5-inch iMac - Thunderbolt 3 (USB-C), 27-inch iMac - Thunderbolt 3 (USB-C), iMac Pro, Mac mini - Thunderbolt 3 (USB-C)