{
 "id": "smartwool-classic-all-season-merino-1-4-zip",
 "name": "Smartwool Classic All-Season Merino Base Layer 1/4 Zip",
 "brand": {
  "name": "Smartwool",
  "url": "https://agenticrecs.com/brands/smartwool/"
 },
 "model": "Classic All-Season Merino Base Layer 1/4 Zip",
 "department": {
  "id": "running",
  "name": "Running",
  "url": "https://agenticrecs.com/running/"
 },
 "category": {
  "id": "running-base-layers",
  "name": "Running base layers & tops",
  "url": "https://agenticrecs.com/running/base-layers/",
  "json_url": "https://agenticrecs.com/running/base-layers/index.json",
  "schema": "running-apparel"
 },
 "subtype": "lightweight merino quarter-zip",
 "msrp_usd": 105,
 "msrp_note": "Men's list price on smartwool.com; the page also shows a $57-$105 range across variants, so some colors may be discounted. Women's price not checked. The crew version is $100 per Treeline.",
 "price_tier": "Mid-range",
 "price_checked": "2026-10-26",
 "attributes": {
  "fits": [
   "men",
   "women"
  ],
  "warmth": "light",
  "wind": "none",
  "water": "none",
  "visibility": "none",
  "temp_range_f": [
   35,
   55
  ],
  "temp_range_c": [
   2,
   13
  ],
  "temp_basis": "estimate"
 },
 "awards": [
  {
   "label": "Best overall",
   "guide": "cold-weather-running",
   "chapter": "base-layers",
   "url": "https://agenticrecs.com/guides/cold-weather-running/base-layers/"
  }
 ],
 "summary": "The most consistently recommended merino base layer for winter running right now: thin enough to wear alone when it's merely chilly and easy to vent through the zip, but it needs a shell or midlayer once it gets truly cold.",
 "best_for": "Runners who want one odor-resistant merino top that works alone in mild cold and as a base layer under a jacket in winter.",
 "not_for": "Anyone who needs standalone warmth below freezing or a rugged top that shrugs off abrasion.",
 "downsides": [
  "Little warmth on its own in real cold",
  "OutdoorGearLab raised durability concerns about the thin fabric",
  "Treeline found it less technical than some vented or hybrid rivals"
 ],
 "where_to_buy": [
  {
   "retailer": "Smartwool (men's)",
   "url": "https://www.smartwool.com/en-us/men/base-layers/tops/mens-classic-all-season-merino-base-layer-1/4-zip/SW002819.html",
   "affiliate": false
  },
  {
   "retailer": "Smartwool (women's)",
   "url": "https://www.smartwool.com/en-us/products/womens-classic-all-season-merino-base-layer-1-4-zip-boxed-sw002827",
   "affiliate": false
  }
 ],
 "materials": "88% merino wool, 12% recycled nylon",
 "style_number": "SW002819",
 "key_features": [
  "150 g/m² merino-nylon jersey",
  "Quarter-zip with 8 in center-front zipper (men's M)",
  "Slim, close-to-body fit",
  "Odor-resistant merino",
  "Same fabric also sold as a crew"
 ],
 "specs": {
  "Fabric weight": "150 g/m²",
  "Fit": "Slim",
  "Neck": "1/4-zip, 8 in zipper (men's M)",
  "Thumbholes": "No",
  "Odor control": "Merino; brand lists odor resistance"
 },
 "official_url": "https://www.smartwool.com/en-us/men/base-layers/tops/mens-classic-all-season-merino-base-layer-1/4-zip/SW002819.html",
 "sources": [
  {
   "publisher": "iRunFar",
   "title": "Best Cold Weather Running Gear of 2026",
   "url": "https://www.irunfar.com/best-cold-weather-running-gear",
   "date": "2026-10-21",
   "finding": "Named the Classic All-Season 1/4 Zip ($105) its best base layer shirt for winter running, citing versatility on its own in mild cold or under a jacket, plus the zip and high collar for managing heat."
  },
  {
   "publisher": "Treeline Review",
   "title": "Best Base Layers of 2026 (Long-Term Tested)",
   "url": "https://www.treelinereview.com/gearreviews/best-base-layers",
   "date": "2026-02-21",
   "finding": "Rated the Classic All Season (crew tested, quarter-zip also offered) Best Overall at $100, praising durability, versatility, sizing and odor resistance through ultras and high-output trail runs; noted it is less technical than some competitors."
  },
  {
   "publisher": "OutdoorGearLab",
   "title": "Best Base Layer (GearLab men's guide)",
   "url": "https://www.outdoorgearlab.com/topics/clothing-mens/best-base-layer",
   "date": "2026-04-01",
   "finding": "Gave the women's Classic All-Season crew a Best Buy and called the line a good fit for runners training through cold months; downsides were durability and limited standalone warmth."
  }
 ],
 "evidence": {
  "specs_from": "https://www.smartwool.com/en-us/men/base-layers/tops/mens-classic-all-season-merino-base-layer-1/4-zip/SW002819.html",
  "reviews_summarized": 3,
  "tested_by_site": false
 },
 "guides": [
  {
   "guide": "cold-weather-running",
   "chapter": "base-layers",
   "url": "https://agenticrecs.com/guides/cold-weather-running/base-layers/"
  }
 ],
 "last_verified": "2026-10-26",
 "url": "https://agenticrecs.com/products/smartwool-classic-all-season-merino-1-4-zip/",
 "markdown_url": "https://agenticrecs.com/products/smartwool-classic-all-season-merino-1-4-zip/index.md",
 "json_url": "https://agenticrecs.com/products/smartwool-classic-all-season-merino-1-4-zip/index.json"
}