Amazon is experimenting with a new delivery service called Seller Flex intended to make more products available for free two-day delivery and relieve overcrowding in its warehouses. A version of Seller Flex first made its appearance two years ago in India, but now it looks as though Amazon is bringing the service to the U.S. as well. Trials have already begun on the West Coast, while a larger rollout has been slated for 2018. This would represent a major break from longtime delivery partners United Parcel Service (UPS) and FedEx.