Verdict from 36 user reviews

8 reasons to buy

  • The offered a reliable grip on slick mud and rain-soaked rocks, a runner reported.
  • Several runners noted that the upper material was very breathable.
  • The shoe provided adequate support in the Achilles area, said a buyer.
  • A couple of customers mentioned that the Agility Fusion Flex looked stylish.
  • Many users claimed that the shoe was true to size.
  • One wearer was impressed with how the shoe relieved their stress on the joints.
  • The toe box was spacious, stated a runner.
  • The Merrell Agility Fusion Flex delivered remarkable ankle stability, according to a commenter.

2 reasons not to buy

  • Some of the seams caused irritation and blisters, a user commented.
  • One wearer felt an unusual lump under the shoe, which felt uncomfortable.

Bottom line

The consensus among runners is that the Merrell Agility Fusion Flex was a reliable trail running shoe; this was evidenced by positive comments regarding support, stability, and traction. While the fit was spot-on, a few experienced discomforts while wearing the shoe. In summary, the Merrell Agility Fusion Flex was an impressive runner that excelled on outdoor adventures.

Tip: see the best trail running shoes.

Good to know

  • The Merrell Agility Fusion Flex is a running shoe that’s designed for the neutral pronator. It has also been configured to work on the trails. It makes use of a semi-aggressive outsole to provide traction over the surfaces. Forefoot flex grooves encourage the natural flexibility of the wearer’s foot.
  • Underfoot cushioning is handled by a full-length foam. It is also tasked with shielding the foot from irregular surfaces and sharp trail debris. A removable footbed contributes more support.
  • A breathable mesh provides breathable coverage for the foot. Reinforcing this material is a synthetic leather cover that’s also meant to stave off the potentially debilitating effects of exposure to the trails. There are additional elements that are designed to hold the foot in place and prevent it from quivering inside the foot-chamber.

Regular measurements were used when the Merrell Agility Fusion Flex was made. Its sizing scheme accommodates the usual choices of consumers. When it comes to width, the options are B – Medium for women and D – Medium for men, and it means that it caters to those who have medium foot-dimensions. The semi-curved shape of this running shoe follows the natural curve of the human foot.

The outsole unit of the Merrell Agility Fusion Flex features a full-length rubber compound known as the M Select™ GRIP. Its job is to protect the midsole from the abrasive nature of the trails. It is also responsible for surface traction.

There are gripping lugs patterned on the external pad. These protrusions are meant to heighten grip over the trails, particularly considering upward and downward traversals.

Flex grooves in the forefoot section allow the platform to bend in conjunction with the joints of the toes. Such a mechanism invigorates the toe-off phase of the gait cycle.

The platform of the Merrell Agility Fusion Flex is comprised of the FLEXconnect™. This full-length ethylene vinyl acetate foam has the purpose of cushioning the landing impact and energizing the toe-off. It has integrated flex grooves in its construction to enable the natural flexibility of the foot.

An EVA footbed adds some more cushioning for the runner. It can be removed or replaced with a custom insert of the runner’s choosing.

Mesh serves as the primary material of the Merrell Agility Fusion Flex’s external façade. It’s a breathable cover that maintains a cool yet secure environment for the foot.

Synthetic leather serves as the overlay system. It’s stitched to the mesh, bolstering it and keeping it protected against the elements. It also helps the traditional lacing system when it comes to locking the foot in place.

A soft fabric serves as the internal sleeve. It staves off skin irritation with its smooth and non-layered construction.


How Merrell Agility Fusion Flex ranks compared to all other shoes
Bottom 2% trail running shoes
All trail running shoes
Bottom 4% Merrell running shoes
All Merrell running shoes
Bottom 2% neutral running shoes
All neutral running shoes


The current trend of Merrell Agility Fusion Flex.
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Jens Jakob Andersen
Jens Jakob Andersen

Jens Jakob is a fan of short distances with a 5K PR at 15:58 minutes. Based on 35 million race results, he's among the fastest 0.2% runners. Jens Jakob previously owned a running store, when he was also a competitive runner. His work is regularly featured in The New York Times, Washington Post, BBC and the likes as well as peer-reviewed journals. Finally, he has been a guest on +30 podcasts on running.