We spent 6.6 hours reading reviews from experts and users. In summary, this is what runners think:

8 reasons to buy

  • This is a road racing flat that offers a barely there feel, says some of the testers.
  • The glove-like feel is nice and secured, and there is no slippage is experienced, as commented by some testers.
  • The toe box is great for wider forefoot runners.
  • The M Select FRESH keeps odor off by maintaining a healthy environment for the foot.
  • It is a flexible shoe.
  • The Protective Toe Cap efficiently shields the forefoot area from incoming debris or hard surfaces.
  • Forefoot strikers can easily take advantage of its no-bulk design.
  • It has a lightweight nature.

3 reasons not to buy

  • The outer tread of this running shoe began to come off for some runners after only a few months.
  • The minimal cushioning left some runners feeling some discomfort when traversing the trails.
  • There were complaints saying that the Toe Cap kept hitting the toes of those wearing it, causing discomfort and irritation.

Bottom line

The Merrell All Out Flash is a versatile running shoe for different running routines. Speed running is a lot easier and more efficient thanks to this model, provided that the runner employs a minimalist or barefoot running style. Because of the lack of cushioning, it is not for heavy runners and runners with concerns with foot pronation, but it works well for neutral runners.


Terrain: Road
Arch support: Neutral
Weight: Men: 6.9oz | Women: 5.2oz
Heel to toe drop: Men: 8mm | Women: 8mm
Pronation: Neutral Pronation
Arch type: High arch
Strike Pattern: Midfoot strike
Distance: Competition
Heel height: Men: 17mm | Women: 17mm
Forefoot height: Men: 9mm | Women: 9mm
Brand: Merrell
Type: Low drop
Width: Men: Normal | Women: Normal
Price: $110
Colorways: Blue, Grey, Purple
Small True to size Large
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Among the better Road running shoes

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89 / 100 based on 1 expert reviews

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  • Merrell’s reputation, when it comes to lightweight shoes with numerous minimalist features, continues to grow in the All Out Flash. The raised heel gives it more protection on the road, but still maintains that nimble feeling when looking for more speed. With a decent stack height and a medium 6mm heel offset, Merrell enables a smooth and effective rolling of the foot from impact to take off.
  • The All Out Flash offers an upper that sticks like a second skin for unbelievable next to skin feel. While there is plenty of natural movement allowed in this shoe, the midfoot is securely locked in while the heel lock holds that part from any slippage.
  • Merrell’s aim to add cushioning in the All Out line gives this shoe better cushioning for such a lightweight shoe. As this has improved cushioning, it can also be a very solid option for uptempo trainings or daily long-distance runs.

Merrell made the fit pleasantly snug in the heel to the midfoot before it becomes a wide forefoot. Road racing shoes that offer this kind of fit usually benefit a large number of runners as it allows plenty of room for the toes to splay. Medium is the available width of the All Out Flash. Sizing bang on in this shoe and offered from 7 to 15 for the men’s and 5 to 12 for the women’s.

The lugs in the outsole are moderately aggressive and covered by Merrell’s own M Select Grip outsole. With this kind of lug a configuration and the sticky nature of the rubber in the outsole, runners are assured of a bite that makes runners very confident.

The minimal stack height houses the Merrell-exclusive UniFly midsole, which is made of premium EVA and proprietary elements to form a lightweight, durable, and very responsive midsole foam.

A durable and incredibly breathable AirMesh covers a large majority of the upper. TPU overlays provide structural support and a more dialed-in foothold. A durable and flexible toe bumper protects the foot from bruises. Merrell also gives option to runners who are looking for more cushioning as it has a 2MM insole. Regular laces called the Omni Fit by Merreell enhance personalized fit and comfort.


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.