For late 2013-15 MacBook Pro and 2013-15 MacBook Air.
The OWC kit included the 1 TB upgrade drive and an external housing for the 256 GB drive originally in my (dear departed) MacBook Pro.
The 1 TB drive is 3 years old. The 256 GB drive was the original one in my late 2014 MBP. The external housing is a neat compact unit that OWC designed to hold the original Apple drive after it had been swapped out for the OWC upgrade.