That said, for a performance-focused training shoe, I did not mind the firmer feel, as it helped contribute to this shoe's peppy ride.
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But I know some customers will be frustrated with the heavier weight of the Zoom Fly 4, especially those who want this shoe to be a race-day option, and I believe this is an area that Nike could address with future iterations.
In addition, the Flywire cables, located in the midfoot, provide more support.
Upper Michael: The upper here is sort of odd; it has a really snug Flyknit collar that made me think Sam had sent me the wrong size! Its sleek design and good performance make it a solid competition shoe for the half or full marathon.
The tongue and the collar are made of this stretchy, knitted Flyknit which is denser and less breathable than the mesh.