First none of Seagate thunderbolt adapters come with a cable.
Here are the speed results I obtained 1tb portable hard drive. I slid it into the seagate thunderbolt adapter. It fits very snug. I backed up some video files to the drive.
Speed test results are:
Reads in/second: 76
Reads out/sec: 83

I also have the seagate backup plus desktop hard drive in 3tb and the speeds were slightly faster with the desktop version.

I plugged in a Lacie 2tb hard drive into the port on the back of the adapter (daisy chain) and this feature worked well with no loss in speed during transfer test.

Would have rated a star higher if seagate would include some sort of Thunderbolt cable.