Updated October 18, 2026. Prices checked October 18, 2026.
Three long-sleeve base layers cost more than $100 and have an independent review. The Assos Winter LS Skin Layer leads at $140. Cyclingnews calls it the best winter base layer, and road.cc rates it very highly for warmth and wicking. The Rapha Merino is $120 and warmer to wear, but BikeRadar and road.cc both note that merino holds more sweat than synthetics. The Giro Chrono is $109.95 on Amazon, and its only independent test is an older BikePerfect one.
How these scores are built. Base layers are judged mainly on breathability, which counts for 45% of the score. Comfort and fit counts 25%, and the other two criteria count 15% each. Based on: Independent reviews by Cyclingnews, road.cc, BikeRadar and BikePerfect, manufacturer specifications and prices read on Jenson USA, Backcountry, Rapha and Amazon. The BikePerfect test is older than the others. Breathability comes from OutdoorGearLab's and GearJunkie's breathability scores where they cover the product, and from our estimate where no test scores it. We do not test products in person. 8 source pages are linked under the 3 products so you can check each finding. How we score.
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Product
Best for
Breathability
Score
1
Assos Winter LS Skin Layer P1
Best winter base layer overall
8.5
8
2
Giro Chrono Long Sleeve
Dry, stretchy synthetic
8
7.5
3
Rapha Merino Base Layer Long Sleeve
Best odor control
6.5
7.3
01
Assos Winter LS Skin Layer P1
Best winter base layer overall, $140.00
8/10
Standout strength. Cyclingnews names it the best winter base layer overall, and road.cc rates it very highly for warmth and wicking.
Breathability 45%
8.5/10
Comfort and fit 25%
9/10
Odor control 15%
6.5/10
Durability 15%
6.5/10
Pros
Cyclingnews calls the fit and feel the best of any cycling base layer in its guide, a wrinkle-free second skin with a raised neck, and says it wicks moisture well.
road.cc rates it very highly for warmth and wicking, and rode it alone under a jacket down to minus 3 degrees C.
Cons
Cyclingnews lists the high price as the one drawback and tells buyers to check Assos sizing before ordering.
road.cc says the high collar can run warm in mild weather. Neither review gave a durability finding, so that score is a neutral estimate.
BikePerfect named it the best winter base layer overall and calls it super dry, snug and soft, with a close, articulated fit for use from September through April.
It is a nylon, polypropylene and elastane blend with a lightly brushed inner face.
Cons
BikePerfect lists the high price as the one drawback. The guide was first published in 2023, and Cyclingnews does not list the Chrono.
Amazon shows 3 owner reviews, so there is little owner evidence. Synthetic fabric holds odor more than merino, and no review gave a durability finding.
Cyclingnews names the Rapha Merino its best short-sleeve merino base layer and says the fit suits a range of riding styles. BikeRadar gave the short-sleeve version 4 out of 5 and calls it a soft, odor-free temperature regulator.
Rapha says it is 100% merino wool with flatlock seams, which road.cc found impossible to feel.
Cons
BikeRadar and road.cc both note that merino holds more moisture than synthetic fabric when you sweat hard, and road.cc prefers it for winter.
The long-sleeve version has no dedicated review. Cyclingnews and BikeRadar tested other sleeve lengths, so the scores carry more doubt.
We could not find reliable independent tests for these products, so they have no score and no rank. We list one only when owners give it at least 4 stars out of 5 across at least 50 reviews. Owner reviews can be incentivized or unverified, so treat them as a weaker signal than the tests above.
Smartwool Classic Thermal Merino Base Layer, Crew$125.00. Rated 4.6 out of 5 from 794 reviews on Amazon.A general outdoor merino top. The price is the regular one on REI, and Amazon's price changes by color and size.
Smartwool Classic Thermal Merino Base Layer, Quarter Zip$130.00. Rated 4.7 out of 5 from 188 reviews on Amazon.A general outdoor merino top with a front zip. Some colors sell for less.
How we picked
Each score comes from independent reviews (Cyclingnews, road.cc, BikeRadar and BikePerfect), manufacturer specifications and the price at the retailer named under each product. We do not test base layers in person. Ratings are our assessment of what the reviewers report. Merino scores high on odor and lower on breathability, synthetics the other way round, and where a review says nothing about durability we use a neutral estimate.
The Assos has two independent reviews of the exact top. The Rapha and Giro reviews cover other sleeve lengths or an older test, so their scores carry more doubt.
What we left out
Smartwool Merino 250 ($125), Capo Super Corsa merino ($110), Pearl iZUMi Pro Alpha ($175) and Assos EQUIPE Winter Skin Layer ($235): US prices read, no independent cycling review found.
MAAP Thermal ($100): belongs to the mid-range ranking.
Spatz Basez Extreme: Cyclingnews rates it, but its store showed euros.
Gorewear base layers: the brand closed its store.
What to look for
Synthetic for the fastest drying, merino for the least odor
A snug fit with a raised neck for winter, and a larger size when a brand cuts small
Flat seams that do not rub on long rides
Questions
Why are only three products scored?
Other tops over $100 had a US price but no independent cycling review we could read: Smartwool Merino 250 ($125), Capo Super Corsa merino ($110) and the Pearl iZUMi Pro Alpha ($175). Spatz Basez Extreme sells in euros on its own store and has no US price we could read.
Why is the Assos priced at $140?
Jenson USA and Backcountry both list the Winter Long-Sleeve Skin Layer at $140. A newer Assos EQUIPE Winter Skin Layer P1 lists at $235, and we found no independent review of it.
Where do the prices come from?
The shelf price on Jenson USA, Backcountry, Rapha or Amazon on October 18, 2026. Both stores ran sales that week, and we ignored them.