For example, it has far less exoskeletal structure than the UltraBoosts. Instead of an exterior heel cup that wraps all the way around, the PureBoost has heel “pads” located on either side of the shoe. The sole has the same technology as the UltraBoost, but a bit less defined.

HOW IS BOOST MADE? To create Boost, thermoplastic polyurethane particles are expanded to form closed cells around tiny pockets of air. The resulting product is known as expanded thermoplastic polyurethane—or eTPU, for short.

Boost is a technology that can hold up for mile after mile without any loss of performance. At the same time, Boost is flexible enough to provide a silky smooth ride — no matter what pace you're setting. But we can't talk about Boost without talking about energy return — the fifth and most famous benefit of Boost.

Responsive cushioning and incredible energy return make Ultraboost shoes essential for runners who want top-notch comfort and support.