A comfortable and lightweight Merino layer that does an incredible job at regulating body temperature — keeping you warm when the digits drop and breathing terrifically when your heart rate is pumping. Created for high output activities in cool to cold weather, the SmartWool Merino 150 Bottoms are a super versatile pair of long underwear that can be used all year long and will perform at the highest levels. We suggest using them for backcountry skiing, trail running, walking your dog, reading a book in a log cabin, eating cereal, winter desert climbing, and backpacking — now that's a do-everything layer! These were one of the pairs that we had a tough time not giving an award. A really nice fit with a simple and efficient seam design and super comfy waistband, these bottoms became a go-to partner in crime anytime we were heading out to play. The downside, as always with Merino, is we wish they were a little tougher.
SmartWool Merino 150 Bottoms Review
Compare prices at 2 resellers Pros: Warm, lightweight, breathable, versatile, comfortable, great thermoregulation
Cons: Not very durable
Manufacturer: Smartwool
Our Verdict
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SmartWool Merino 150 Bottoms | |||||
| Awards |  |  | |||
| Price | $59.99 at Backcountry Compare at 2 sellers | $110.00 at Amazon | $59.95 at Amazon Compare at 2 sellers | $89.00 at Backcountry Compare at 2 sellers | $59.00 at REI Compare at 3 sellers |
Overall Score  |
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| Star Rating | |||||
| Pros | Warm, lightweight, breathable, versatile, comfortable, great thermoregulation | Soft next-to-skin, super warm for its weight, durable and all-natural | Ultra-lightweight, fast wicking and quick drying, breathability | Warm, super comfy, durable, great fit, versatile, don’t stretch out | 100% recycled polyester, light fabric weight, impressive loft and warmth |
| Cons | Not very durable | A touch heavy for fabric weight, slow to dry after washing | Thin material is not warm, articulated seams could create constrictions | Pricey, below-average breathability | Questionable durability, saggy bottom |
| Bottom Line | A fantastic pair of lightweight Merino bottoms that provide impressive warmth without being too hot, breathe extremely well and are very comfortable. | Undeniably comfortable, warm, and breathable, this pair of long underwear has it all…even knee-pads. | The future of fast-and-light long underwear. | An outstanding synthetic bottom that offers great warmth, extreme comfort, a stellar fit, and durability to last; built for cold conditions, these cozy bottoms are perfect for everything from winter trail running to cold resort skiing. | Warmer than most, lighter than the rest, this pair of long underwear re-defines what is possible from a synthetic base layer. |
| Rating Categories | SmartWool Merino 150 Bottoms | Ortovox Rock'N'Wool Pant | Enigma Bottoms | Arc'teryx Rho LT Bottoms | Capilene Midweight Bottoms |
| Warmth (30%) | |||||
| Breathability (30%) | |||||
| Comfort And Fit (30%) | |||||
| Durability (10%) | |||||
| Specs | SmartWool Merino... | Ortovox... | Enigma Bottoms | Arc'teryx Rho LT... | Capilene Midweight... |
| Material | 87% Merino wool / 13% Nylon core | 100% Merino wool | driRelease (88% recycled polyester, 12% wool) | Torrent (84% polyester, 16% elastane) | 100% Recycled polyester with HeiQ Fresh |
| Fabric Weight | 150 g/m² | 185 g/m² | 155 g/m² | 175 g/m² | 147 g/m² |
| Weight (size M) | 4.94 oz (size S) | 6.58 oz | 4.97 oz | 5.57 oz (size S) | 5.88 oz |
| Insulation Weight | Lightweight | Midweight / Lightweight | Lightweight | Lightweight | Midweight / Lightweight |
| 3/4 Boot-Cut Available? | Yes | Yes | No | No | No |
| Fly? | Yes | No | Yes | No | Yes |
| Dryer safe? | Yes | No | No | Yes | Yes |
Our Analysis and Test Results
A stellar lightweight Merino base layer that holds true to SmartWool's reputation of being the masters of Merino. Thoughtfully built with great warmth and breathability, these bottoms are an all-around champion for everything except bitter colds.
Performance Comparison
Warmth
For how thin these are, they are impressively warm. Merino has an incredible ability to provide insulation even with a thinner fabric. These do a great job of insulating when they are under a shell and able to hold onto heat. If you wear them with a thin, breathable pair of pants, they will be less warm which is why they are so versatile. Put them under an insulated pant for maximum warmth, a water-proof shell for medium warmth, and a light pair of breathable hiking pants for maximum breathability. We loved them for backcountry skiing when the temperatures weren't frigid and everything else that lives above ice cold. Backpacking, lounging, traveling, hiking, and alpine climbing — this pant does it all and is a perfect weight for active endeavors in everything except arctic conditions.
Breathability
These excel at breathability and wicking away sweat. The inherent qualities of awesomeness that Merino already possesses are increased by the thinner weight fabric. Take merino's ability to breathe, wick sweat, and dry quickly and multiply it and you have the SmartWool 150 pant. Skinning in warm conditions in the Rockies, these were the perfect layer, breathing and wicking away sweat on the uphill slogs, always keeping us dry but maintaining warmth when clouds rolled in and the temperatures dropped.
Comfort & Fit
A super comfortable pair of bottoms, we found they were good for wearing all day. They didn't stretch out as significantly as other Merino layers like the after heavy use. Maybe due to the fact that SmartWool wrapped a Merino fiber around a nylon core for added durability and shape retention, no matter the reason we aren't complaining. Comfortable next to skin, they fit tight like a traditional base layer.
They have minimal flatlock seams that you don't even notice are there. A single inseam runs the length of the pant meeting up with the crotch. There is a tiny bit of crotch sag, but if you wear them at your bellybutton, they fit like a glove. The wide waistband is comfortable for all-day wear. The ankles are really tight and require some care pulling over your heal, or you could easily rip the thin merino fabric. Overall, great comfort and fit. One of our head testers, at 6 ft and wearing a small (30in waist), they were a tad bit short exposing a little bit of ankle. If we could change anything, it is to reduce the minimal crotch sag and lengthen the legs a bit.
Durability
Durability — the Achilles heel of the praiseworthy warrior of base layers, merino wool. These bottoms are no exception, they just aren't that durable. SmartWool attempted to increase durability by wrapping the Merino fabric around a nylon core which we think helps with shape retention and overall longevity but when it came down to our merciless abrasion test, we smoked a hole right through these bad boys.
Other Merinos of a slightly thicker fabric weight still bear the same scars from our abrasion test. As always with Merino wool, don't climb granite chimneys in your merino chonies and don't put them in the dryer. If you follow these two easy rules, a Merino base layer can last you for years of use.
Value
This pair falls a little above the middle of the ground for pricing. These bottoms provide a solid balance of breathability, with just the right amount of warmth. Considering their ultra-soft next-to-skin feel — so soft that you might not want to ever take them off — combined with the quality of performance, they are well worth the price.
Conclusion
Our conclusion… these things rock. A great versatile layer made of comfortable lightweight Merino wool that breathes exceptionally well and carries impressive warmth for how thin it is, we really enjoy these bottoms and think you will too!
— Roland Mott