It’s great to see the shoes coming with the new heel area design. Made to bend away from the Achille’s tendon, the shoes feel great on long runs, which can also work to improve their racing profile. With a single airbag which runs from the heel to the forefoot, the shoes are now better in terms of cushioning, with a more unitary feel. The difference is not too big for the previous generation, but I feel they are a bit smoother overall. Flexibility is still great though. This great flexibility is also based on the fact that Nike moved the bottom eyelets up.