The upper of the Flow Synchronicity has been designed with minimal layers, for close-to-foot containment. This isn’t a bootie-upper — there’s still enough stretch to prevent irritation or hot spots — but it’s definitely designed to hug the foot and keep it in place on the run.

In my opinion, the best design feature when looking at the upper is the heel grip. Despite the shoe coming up a little long for me, the shaped heel really did keep my foot from sloshing around in the shoe, and it was comfortable on the run.