Merrell MTL Long Sky 2 trail running shoes review: lock in for technical trails

Tackle the toughest trails in any conditions with these lightweight, versatile and breathable trail runners featuring a locked-in fit and mega grip soles

Merrell Long Sky MTL 2 on the trails
(Image: © Julia Clarke)

Advnture Verdict

These trail running shoes are built for endurance and stability in all conditions, with a comfortable locked-in fit, quick-drying mesh uppers and excellent grip keeping you on your feet come rain or shine.


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    Roomy toe box with reinforcements

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    Breathable and quick drying upper

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    Internal bootie for locked-in fit

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    5mm lugs handle slick terrain nicely

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    Good cushion and decent trail feel

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    Gaiter attachments

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    Vegan-friendly and some recycled materials


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    Not waterproof

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    Midsole may not be thick enough for long distance runs

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    Low drop may not work for heel strikers

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Merrell MTL Long Sky 2 trail running shoes: first impressions

Merrell describes its latest trail running shoes as ready-for-anything, and after testing them out, we’d have to agree. These trail runners are lightweight for when you want to go fast and far and with an internal bootie that pulls on like a sock, you get an instant locked-in fit without having to retie your laces. Easy to pull on, the snug fit around the cuff is balanced with a roominess around the toe box which adds to the light, airy feel of these shoes.


• List price: From $140 (US) / £115 (UK)
• Unisex: Men’s and women’s specific fit available
• Weight: 1lbs 4oz / 560g
• Materials: 5mm Vibram MegaGrip soles, EVA foam insole with 100% recycled top sheet, FloatPro Foam midsole  
• Drop: 4mm
• Colors: Tangerine
Compatibility: Technical trail running  

Breathable mesh uppers with a TPU overlay manage to be durable and keep your feet cool when you’re out in hot weather, plus they’re quick drying for when you’re splashing through puddles. Once you hit uneven, rocky terrain, you’ll really appreciate the stability provided by the low 4mm drop combined with 5mm lugs on the MegaGrip soles, which hold up even in slick conditions. They’re not waterproof, but with gaiter attachments you can easily protect your feet in a deluge. 

The FloatPro Foam midsole strikes a nice balance between cushioning and a decent trail feel. These aren’t big and bouncy for super long runs, nor are they barefoot and minimal – they’re great for handling technical terrain and mixed conditions with confidence.

Merrell MTL Long Sky 2 trail running shoes: in the field

Merrell Long Sky MTL 2 on the trails

The FloatPro Foam midsole strikes a nice balance between cushioning and a decent trail feel (Image credit: Julia Clarke)

These shoes arrived just as the uppers on my last pair of trail runners separated from the sole, so I was eagerly anticipating them. I’ve been hiking in Merrell shoes for a couple of years and really like their handling on the trails, waterproofing and robustness, so I had high hopes for their running shoes and I have not been disappointed.

I will admit I was a little skeptical of the internal bootie which gives the shoes a sock-like construction. I have a pair of hiking shoes with this same construction and with high arches, I find them quite hard to pull on. However, these ones slip on fairly easily and once on, I get a tight, firm, locked-in heel without having to tie a heel lock, which is great for running over rocky terrain.

Once I headed out in these, there were two things I noticed straight away that I really like. The first is that they have a really perceptibly airy feel thanks in part to the breathable uppers, but mostly due to the extra room in the toe box. My previous running shoes have tended to be a bit snugger around the toes, which can actually impact my ability to use my toes and move optimally, and I was surprised that these have so much room while being so snug around the cuff. Anyway, the result is that they feel really comfortable, especially on hot days. They also have a little reinforcement around the toes for bashing into rocks (or long talons).

Merrell Long Sky MTL 2 on the trails

The toe box is wide and airy, with reinforcements for when you bash up against a rock (Image credit: Julia Clarke)

The other thing I really like is the FloatPro Foam midsole, which I found strikes a perfect balance between cushioning and trail feel. I’ve been running in big, bouncy shoes for the past two years which felt very cushy, but meant I didn’t get much sensation of the ground beneath my feet, and while I don’t like a lot of trail feel, I appreciate getting just a little more with these. Initially, I thought they wouldn't be as comfortable as a result but I definitely prefer them. The low drop and good lugs means I feel really stable, even when I’m on tough terrain.

I’ve had these out in a few downpours and, no surprise, the Vibram soles definitely deliver the mega grip they promise. The uppers aren’t waterproof (which helps with breathability) but they dry quickly and though I haven’t tried them out, they come with hooks in the heel for your gaiters if you’re out for a long distance dash in a deluge. 

Overall, I think Merrell has done a fantastic job of combining just about everything I’d want in a trail runner, from weight and breathability to stability and comfort, for a really technical shoe.

Here’s how they performed:

Sizing and fit

These fit true to size and are snug around the cuff, but roomy around the mid foot and toe box. They might be too wide for narrow feet.

Merrell Long Sky MTL 2 on the trails

These fit true to size and are snug around the cuff but roomy around the mid foot and toe box (Image credit: Julia Clarke)


Locked-in fit prevents rubbing and provides a snug fit, while the mid-sole gives enough cushion for protection against rocky trails without impact trail feel. Roomy toe box gives a light, airy feel.


Breathable mesh uppers are quick drying and offer plenty of ventilation.


Only time can truly tell, but all signs point towards a pretty durable shoe with good construction and TPU lined uppers.

Julia Clarke

Julia Clarke is a staff writer for and the author of the book Restorative Yoga for Beginners. She loves to explore mountains on foot, bike, skis and belay and then recover on the the yoga mat. Julia graduated with a degree in journalism in 2004 and spent eight years working as a radio presenter in Kansas City, Vermont, Boston and New York City before discovering the joys of the Rocky Mountains. She then detoured west to Colorado and enjoyed 11 years teaching yoga in Vail before returning to her hometown of Glasgow, Scotland in 2020 to focus on family and writing.