Update 1.7.1 for World of Tanks is here.
Double-barreled tanks are included, along with the new Demount Kit. You’ll be able to try out three Soviet double-barreled tanks, which each including three different shooting modes. The demount kit will allow you to unmount where you can send your Complex Equipment to the Depot at no cost.
The Demount Kit can be acquired from drops from the Large Reward for Merit. Once you earn an Demount Kit, it’ll be stored in the Stock section under Consumables. It’ll be debited automatically once you’ve used it.
You can learn more about the update here.