Does it support external usb 3.0 HDD 2.5? We can confirm that the USB-C Slim Dock for 24” iMac is compatible with a USB external 2.5" HDD. Related articles What drives are compatible with the Slim Dock? How do I install my SSD drive? Quick Guide & Instructional Manual Is it compatible with the Apple Studio Display? What are the transfer speeds for both the USB-C and USB-A ports and will it support charging? Comments 0 comments Article is closed for comments.