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Merrell MTL Long Sky 2 Review: A Favorite for Fast, Long, Technical Trail Running

(Photo/Sam Schild)
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The Merrell MTL Long Sky 2 trail running shoes are lightweight, all-around trail runners that excel in versatility and grip.

I’ve been testing a pair of the new Merrell MTL Long Sky 2 trail runners for the past month, and they’ve become my go-to trail runners here in Colorado for technical trails. I wore these shoes while I summited five peaks in 2 days, during a 28-mile trail run on the Maroon Bells Four Pass Loop, and on many more 10-15-mile trail runs of the Colorado Front Range and beyond.

Now that I’ve put close to 200 miles on these shoes, I’m stoked to have found one of the most versatile trail runners I’ve ever worn.

In short: The Long Sky 2s aren’t a drastically different shoe than the original Long Skys, but several key improvements make a great shoe even better. The Long Sky 2 trail running shoes differ from version 1.0 of these shoes in the following ways:

  • 4 mm heel-to-toe drop, compared to 8 mm on the original Long Skys
  • Updated FloatPro foam midsole is more dense and lightweight
  • 10% lighter
  • Better water evacuation
  • Now made with some recycled materials

The Long Sky 2s are at home moving fast on hardpacked dirt and scrambling up rocky ridges, grippy enough for wet conditions, and have just enough cushion to be comfortable while still feeling stable.

Merrell MTL Long Sky 2 Review

What’s New on the Long Sky 2

Merrell MTL Long Sky Review
(Photo/Sam Schild)

The Long Sky 2 trail runners have 4 mm of drop from heel to toe, half the amount of drop that the originals had. This means more stability since your foot will be closer to flat. The minimal drop, along with the not-too-tall 23.5-19.5 mm stack height, makes these shoes feel very stable over rocky terrain.

Heel-to-toe drop ultimately comes down to preference, but I think the 3-5mm range is the goldilocks zone for trail runners. My running form isn’t perfect, especially as I get tired, so I often strike first with my heels. I think some drop is great for this reason. On the other hand, too much drop makes me feel like I’m falling forward, especially on descents.

On the final mile of the 50k Four Pass Loop trail run, I found myself moving quickly downhill over a trail that was more talus than dirt. I didn’t fall or slip, not once. The minimal drop on these shoes certainly helped with this.

FloatPro Midsole

Merrell MTL Long Sky - trail running
(Photo/Sam Schild)

The Long Sky 2 features an updated midsole made with FloatPro Foam, a lightweight and medium-density foam Merrel first used in their Moab Flight trail runners. I like how much these insoles allow you to feel the trail underfoot while still providing enough protection and support to keep your soles feeling good.

Usually, trail feel and underfoot protection from sharp rocks come as a tradeoff: you can have more of one or the other, but not both. This midsole finds the sweet spot with this.

These midsoles are firm enough to allow for a lower stack height and still feel solid. They’re firm, not bouncy, but do have a little bit of spring.

But even though there is less foam underneath you than highly cushioned trail runners, the dense foam protects the soles of your feet from sharp edges and small rocks.

On the Colorado Front Range, most trails aren’t smooth ribbons of dirt. The trails out here are rocky, and most of the rocks are sharp. These shoes are excellent for all those little sharp rocks, despite their low stack height.

Merrell MTL Long Sky 2 Specs

  • Weight: 1 lb., 4 oz., 560 g (size 9.5)
  • Stack height: 23.5-19.5 mm
  • Heel-to-toe drop: 4 mm
  • Lug depth: 5 mm

Lighter Weight

The size 9.5 Long Sky 2 shoes I’ve been testing weighed 9.9 ounces per shoe on my scale when brand new. This is about 10% lighter than the previous iteration of the Long Sky trail runners.

Better Water Evacuation

MTL Long Sky - Water Evacuation
(Photo/Sam Schild)

Merrell claims the new Long Sky 2s retain water 30% less than the previous Long Skys. Though I can’t speak to specific water-retention percentages, I can say these shoes don’t feel particularly heavy for long after you dunk them in water.

After running a route that connects the 14,000-foot peaks Mt. Bierstadt and Mt. Evans via the Sawtooth Ridge, I followed a cross-country route off a saddle through a marsh. There were moments when I was in wet mud up to my knees, and the shoes definitely felt heavier then.

But after a rinse in a stream and a couple of minutes spent walking on dry ground, these shoes felt pretty dry. They’re by no means an instant-drying, water-repelling wonder, but I’d say 30% less full of water coming out of a stream is pretty accurate. And, one-third less water sloshing around in your shoes is pretty good.

Built With Recycled Materials

These shoes now come with 100% recycled laces, tongue webbing, and TPU reinforcements. They’re not made entirely of recycled materials yet, but it’s a start.

What I Like About the Long Sky 2s

Merrell MTL Long Sky - trail running shoes
(Photo/Sam Schild)

These shoes are immediately comfortable out of the box. My first run with the Long Sky 2s was a 5-mile loop in Acadia National Park. The loop was a mix of gravel paths, dirt, and scrambling on smooth rock, with a few very steep downhill sections.

It was a short enough run to not cause problems either way, but after 5 miles was over, these shoes felt like I could easily do another 5 or 10 in them.

Moving on.

These shoes grip. They have 5mm-deep lugs and a Vibram Megagrip outsole, so they provide excellent traction on loose dirt, rocky terrain, and everything in between. I used these shoes to scramble some class 4 ridges and was very impressed.

They’re now my favorites for peak bagging runs with a long approach. They’re great to run in, and the Vibram Megagrip rubber is sticky enough to use for class 3 or 4 pushes to the summit.

Merrell MTL Long Sky - climbing
(Photo/Sam Schild)

These shoes are durable enough to handle lots of rocky ridge-running and scrambling. After close to 200 miles on my first pair, I see no signs of the mesh uppers tearing.

The TPU reinforced points where the mesh upper meets the toe and sides of the shoe are well placed. Usually, by 200 miles of rough trail, I start to see some evidence of the mesh tearing near the midsole, but not with these.

They fit really well, too. The tongue wraps around the top of the foot and extends down to the base of the shoe. This makes these shoes feel secure even when unlaced.

I know some runners who have been wearing these shoes with the laces barely tightened at all. I would only do this on smooth terrain, but that’s still saying a lot.

What I Don’t Like About the Long Sky 2s

There is very little I don’t like about these shoes. I did have to play with the lacing to get a solid heel lock, but that’s the case with a lot of trail runners.

I used the standard heel lock lacing technique at first, but I ended up modifying it slightly, feeding the laces through both of the top eyelets, and then tying them as normal.


The Merrell MTL Long Sky 2 trail running shoes are currently my go-to trail runners for most runs. They wouldn’t be my first choice for runs over 50k, as they lack the cushion I want for a really long day. However, I bet I’ll end up using them for a 50-mile day sometime soon, anyway.

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