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
HDD, SSD or Flash Storage? Which storage option is the best for the Mac Pro? - MacFinder Blog
Touch Bar MacBook Pro models have non-upgradeable SSDs, seemingly under-sized batteries - 9to5Mac