Get OWC Aura and Aura Pro SSDs at MacSales.com (480GB and 960GB).
Previously discussed at announcement, the OWC Aura for the 2013 and later MacBook Air or MacBook Pro Retina is an internal SSD upgrade to 480GB or 1TB*, which is up to 8X as much storage for the MacBook Air, and up to 4X as much for the MacBook Pro Retina.
MPG tested the 960GB Aura in the MacBook Air 6,2. Similar performance is expected when installed into the 13" or 15" MacBook Pro Retina.
Includes a discussion of repurposing the original Apple internal SSD into the optional Envoy Pro USB3 case, as well as thoughts on when and why upgrading make sense.