It's been a while since we had a Nike shoe in the lightweight trainer category, so we're excited to bring in the Zoom Fly 4.  React foam in the midsole plus a carbon plate (similar to the one in the Vaporfly Next% 2, but a bit more flexible) throughout gives this shoe a very responsive, snappy feel.  Durable enough for an everyday trainer, but light enough to be a secondary workout/race option.