The listing, MARVEL EXTRAS - bonus from The Avengers Age of Ultron(read description) has ended.
This is for the code to redeem the bonus Marvel Extras that come with purchasing The Avengers Age of Ultron on 3D Blu Ray. The digital copy is not included. Some of the extras include the digital comics for Black Widow and Hawkeye. Also you can get a free Hulkbuster sticker decal for just the price to ship it. There are a couple more extras too. It's redeemed at more.marvel.com/Ultron.