• 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: 8.5oz
    Women: 8.5oz
  • Heel to toe drop
    Men: 6mm
    Women: 6mm

    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: 30mm
    Women: 30mm
  • Forefoot height
    Men: 22mm
    Women: 22mm
  • 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.

  • First look / Unboxing | Shop Zappos

  • First look / Unboxing | Shop Zappos

Apply to become an expert

Updates to Merrell Agility Synthesis Flex

  • 0% animal products were used in the making of this shoe. With this, Merrell offers a Vegan-Friendly option for those who do not use any animal product in their diet or in the items they are using.
  • The Agility Synthesis Flex has the Merrell Hyperlock technology. This feature is a molded TPU heel film which helps secure the foot in place while the runner is going over the trail. The support it gives is not significant, but it still offers minimal stabilization.
  • The midsole has the FLEXConnect feature – the design on the platform that’s composed of flex grooves that move in dual directions. These grooves allow the midsole to effortlessly adapt to the runner’s movements, making each stride adaptive and easy.
  • The M Select Fresh antimicrobial footbed was added to combat bacteria and moisture from within the shoe. This extra padding keeps the in-shoe environment balanced as it absorbs sweat and eliminates bad odor.
  • On the outsole is the M Select Grip which affords the bottom of the shoe with enough traction to tackle various terrain conditions. Though this outsole was designed for light trail, it gives a decent amount of traction and grip.
  • There’s an extra layer on the midsole that protects the bottom of the foot from sharp rocks or other objects on the trail that can potentially cause injury. It is called TrailProtect.

Merrell Agility Synthesis Flex size and fit

The Merrell Agility Synthesis Flex is available in regular sizes. Runners will be able to purchase the shoe using their usual size preference. Regarding width, the shoe comes in the standard B-medium and D-medium measurements.


The outsole is made of a durable rubber called M Select Grip. It is wear and tear-resistant, prolonging the life of the footwear, as well as bringing a tough layer of protection underfoot. Aside from its durability, it provides the right amount of grip and traction on both wet and dry surface conditions.

On the forefoot area of the shoe’s bottom, phalange-like lugs are placed strategically to mimic the anatomy of the bones on the foot. The placement makes it easier for the outsole to sink into surfaces, even ones that are uneven. The lugs also make the bottom self-cleaning, releasing tiny debris and dirt on its own. Meanwhile, the heel portion has lugs that are closer together to deliver the most hold on different surfaces.


The midsole is made up of a material called EVA which is short for Ethylene-Vinyl Acetate. This dense foam is excellent when it comes to providing enough underfoot comfort, cushioning and shock absorption. It allows runners to have a responsive ride with enough energy return.

On the sides of the EVA foam, dual-directional flex grooves were designed for better flexibility, making runners feel less restricted when it comes to moving. Also, the grooves help with balance to some degree. When the foot is on uneven terrain, the grooves compress to help even out the level of the shoes.

As an extra layer of protection, a pad called TrailProtect was added. Appropriately named, it basically protects runners from rocks that can easily be stepped on while going over the trail, thereby preventing injury or disruptions in the continuity of running.


The upper of the Merrell Agility Synthesis Flex is made up of mesh. It’s a textile that’s comfortable and breathable, letting air circulate within the shoe and minimizing hot spots. It also hugs the foot snuggly without constricting it. The mesh was formed into an eye-catching, chevron pattern with two tones which allow the shoe to stand out.

To reinforce the heel part of the upper, the Hyperlock component was introduced. It is a TPU (Thermoplastic Polyurethane) film found on both sides of the heel, forming one band. It minimally locks the heel down in place, preventing it from moving too much when the runner is moving.

Also reinforcing the upper is the synthetic toe cap. The tip of the shoe is commonly the part that bumps into different objects on the trail. To prevent injury to the toes, the tip was made more durable with a coat of synthetic material, allowing it to withstand impact forces.

Merrell added their trademark M Select Fresh technology as a removable footbed. It naturally keeps odors at bay by making use of reactive microbes that breakdown foot sweat with natural enzymes. The technology absorbs the sweat and eliminates bacteria thereby maintaining a healthy environment within the shoe.