• Discontinued
  • Terrain


    Shoes best for road, track and light gravel. See the best road shoes.


    Shoes best for trail, off road, mountains and other unstable surfaces. See the best trail shoes.

    Good to know

    As long as you stick to the road or path, and if you want just one running shoe, buy a road running shoe.

  • Arch support

    Neutral / cushion / high arch

    Shoes for runners who do not need any additional arch support (Around 50% of runners). Best for people with normal, high or medium high arches. See the best neutral shoes.

    Stability / overpronation / normal arch

    Shoes for runners who need mild to moderate arch support (Around 45% of runners). Best for runners with a low arch. See the best stability shoes.

    Motion control / severe overpronation / flat feet

    Shoes for runners who needs a lot of arch support. Best for runners with flat feet. See the best motion control shoes.

    Good to know

    - Rule of thumb: If in doubt, buy neutral shoes to avoid injuries.
    - More about arch support in this video.
    - Find your arch type by following steps from this video.

  • Use

    Daily running

    Cushioned shoes for your daily easy running. Great comfort. See best shoes for daily running.


    Lightweight shoes good for races, interval training, tempo runs and fartlek. Here are the best competition running shoes.

    Good to know

    If you want just one pair of shoes, buy a shoe for daily running.

  • Price
  • Weight
    Men: 10.4oz
    Women: 9oz
  • Heel to toe drop
    Men: 10mm
    Women: 10mm

    The height difference from the heel to the forefoot, also known as heel drop, toe spring, heel to toe spring or simply drop.

    There are many opinions about what a good heel drop is. We do not recommend any in particular. Lean more in this video.

  • Heel height
    Men: 28mm
    Women: 28mm
  • Forefoot height
    Men: 18mm
    Women: 18mm
  • Width
    Men: normal
    Women: normal
  • Release date
Show more facts


Expert Reviews

Experts are runners, who post reviews at youtube, directly at RunRepeat or at their own websites. Each expert is categorized from level 1 to level 5 based on expertise. See stats on expert reviews and how we calculate scores here.

Are you an expert? Apply to contribute here.

90 / 100 based on 1 expert reviews

  • 90 / 100 | Steve Zilla

    ...I have to say, I am really loving this. Thanks to the new upper material. I never have to break this in. It's fantastic.

Apply to become an expert

Updates to Nike Air Zoom Structure 21 Shield

  • The Nike Air Zoom Structure 21 Shield is a road running shoe that is strategically designed for overpronators. The upper area is constructed using Flymesh and a DWR (durable, water-repellent) coating, which ensure lightweight breathability and protection against mild water infiltration.
  • It features the Waffle lugged outsole that aims to provide added traction and durability. This material is essential in efficiently handling all the runner's running needs.
  • The water-repellent version of the Structure 21 uses the dual-density midsole. This technology offers support and shock absorption.

Nike Air Zoom Structure 21 Shield size and fit

The Nike Air Zoom Structure 21 Shield is a stability shoe that is designed for runners who overpronate. It is best used for road running activities. When it comes to size, the product has a standard shoe length. The available widths are medium for both the men and women's versions.


Utilized in the outsole is the Duralon Blown rubber that is located in the forefoot area. This technology's purpose is to provide enhanced cushioning and comfort.

Along with the Duralon Blown rubber is the Waffle outsole design. This component of the shoe is meant to improve cushioning and multi-surface traction.

It also features the BRS 1000 carbon rubber, the goal of which is to add more grip and durability. This durable rubber material is also used in the new Air Zoom Structure 22.

To provide a smoother ride, Deep Anatomical Flex Grooves are utilized. The purpose of this material is for added mobility and flexibility.


Phylon and Cushlon foams are fused together to create a dual-density midsole. These materials are located on the medial and lateral side to promote a more resilient cushioning and softer feel.

At the bottom of the heel is the crash pad. It is a gender-specific, decoupled unit that aims to reduce impact shock and correct overpronation.

Located in the forefoot area is the Zoom Air unit. It is made up of a responsive insert that is focused on providing a springier cushioning.


The upper area utilizes the 360-degree Reflectivity. This component of the shoe makes it highly visible, especially in low-light conditions.

The Flymesh is composed of monofilament yarns that aim to improve breathability and create a lighter material when compared to previous models. It’s treated with DWR (durable, water-repellent) coating to stave off splashes and mild exposure to water.

The last two eyelets that cover the midfoot have Flywire cables. The goal of these materials is to provide unmatched fit and lockdown while maintaining a lightweight structure.

The Dynamic Fit technology, which includes an internal arch band and the Flywire cables, is integrated into this running shoe. This design is centered on providing an adaptive fit and total lockdown support.

An inner mesh bootie design is added to give a soft and sock-like fit. Notches on the side of the tongue unit allow easy on and off.

The upper also utilizes an internal heel counter. This technology wraps around the Achilles to provide a more secure fit.