Samsung NVM Express SSD Upgrade ab Mac Pro Late 2013 6,1 A1481 | Comtecshop24.net
Amazon.com: 256GB SSD Hard Drive for Apple MacBook Pro Air 11" 13" 15" A1502 A1398 A1465 A1466 (Late 2013-2015) / OSX Sierra/Mac Pro A1481 : Electronics
Apple is using a custom connector for the SSD in the new Mac Pro | AppleInsider