250 GSM is our everyday cold-weather standard — warm enough for winter city days, breathable enough for the trail.
Fabric weight guide
Which merino weight is right for you?
GSM is grams per square metre — how much fabric there is, not a warmth rating. Every weight is the same soft 17.5-micron Australian merino: it wicks sweat before it turns cold, insulates when it is cold and ventilates when it is warm. Lighter fabric breathes and dries faster; heavier fabric holds more heat when you stop moving. Choose by season and by how hard you will be working.
Warm & hot · 60°F+ / 15°C+
Best for: summer hiking, running, cycling, hot-climate travel, everyday tees and office wear; the next-to-skin layer under a 250 when you work hard in winter
Pick this if: you want a shirt that stays fresh for days, dries in an hour and keeps you cooler than cotton in the heat — or you simply run hot
Think twice if: you will mostly be standing still in the cold; on its own a lightweight layer has little insulation to offer
Shop 165 GSM →Cool to mild · 40–65°F / 5–18°C
Best for: spring and autumn as a standalone top, summer evenings, cool-morning hikes and commutes; winter as a base under a mid-layer
Pick this if: you want one merino layer that covers most of the year, or you are unsure between light and mid — this is where most people should start
Think twice if: you run cold and your winter is genuinely cold: go straight to 250
Shop 190 GSM →Cold · 20–45°F / −7 to 7°C
Best for: skiing and snowboarding, winter hiking, cold-weather work, frosty autumn mornings; top-and-bottom sets so your legs are not the weak link
Pick this if: you run cold in fall, want the classic winter base layer, or spend active days below freezing under a shell
Think twice if: you overheat easily on hard uphill efforts — a 165 or 190 underneath, 250 over it, is the better system
Shop 250 GSM →Deep cold · below 20°F / −7°C
Best for: ice fishing, hunting stands, camp at altitude, winter mornings spent waiting rather than walking, a house that never quite gets warm
Pick this if: warmth matters more than breathability, you are chronically cold, or your winter involves long spells standing still outdoors
Think twice if: you will be working hard — it is too warm for a sweaty climb, which is exactly the point
Shop 320 GSM →A base layer works by sitting close to the skin, where it can move moisture — loose is not more comfortable, just slower. Between sizes? Size down for a next-to-skin layer under a shell, size up to wear it on its own or over another layer. Merino stretches with wear and springs back after a wash. Heavier weight is not itchier: itch comes from coarse fibre, and every weight here is the same superfine merino.
Size guide
Size Guide
Our merino has a close, next-to-skin fit by design. If you are between sizes, stay true to size for base-layer use or size up for a more relaxed everyday fit. Free returns within 30 days, so ordering two sizes and sending one back is completely fine.
How to measure
Chest — around the fullest part of your chest, with the tape level under the arms.
Waist — around your natural waistline, with the tape comfortably loose.
Hips — around the fullest part of your hips and seat.
Inside leg — from the top of your inner thigh to your ankle bone.
Measure over light clothing, keeping the tape snug but not tight. Tap any chart below to open it full size.
Men's Base Layer Set
Need different sizes for the top and the bottoms? Build your own set →
Women's Base Layer Set
Need different sizes for the top and the bottoms? Build your own set →
Kids' Base Layer Set
Men's T-Shirt
Women's T-Shirt
Men's Long Sleeve
Same body measurements across 165, 190, 250 and 320gsm.
Women's Long Sleeve
Kids' Long Sleeve
Men's Long Johns
Women's Thermal Leggings
Kids' Thermal Leggings
Men's Half Zip
Women's Half Zip
Merino Wool Socks
Beanies, snoods and balaclavas
Still unsure which size to pick? Email info@merinotech.co.uk with your height, chest and waist and we will recommend a size. Free UK delivery over £49 and free returns within 30 days.
- Free UK delivery over £49
- 30-day free returns
- Ships in 1–2 business days
Description
Experience all-season comfort and style
Crafted from natural Merino wool, this shirt offers unbeatable softness against your skin.
Stay cozy in winter, cool in summer, and enjoy natural odour resistance.
Elevate your wardrobe with this versatile and exclusive piece.
Care
Turn inside out. Machine wash cold on a gentle cycle with like colours and a wool-safe detergent. Do not bleach. Lay flat or hang to dry — do not tumble dry.
Shipping & returns
Free UK delivery on orders over £49. Orders ship within 1–2 business days. 30-day free returns on unworn items with tags attached.
Men's long sleeve base layer
Built for layering, worn on its own
A close, next-to-skin fit with flatlock seams and a long body that stays tucked. Wear it alone on cool days or as the first layer under a shell when it really gets cold.
Size guide
Men's Long Sleeve 320
Fit
A close, next-to-skin fit that is true to size for a base layer. Between sizes? Stay true to size to wear it under other layers, or size up for a more relaxed fit on its own.
How to measure
- Chest – around the fullest part of your chest, tape level under the arms.
- Waist – around your natural waistline, tape comfortably loose.
- Hips – around the fullest part of your hips and seat.
- Inside leg – from the top of your inner thigh to your ankle bone.
Measure over light clothing and keep the tape snug but not tight. Still unsure? Email info@merinotech.co.uk with your height, chest and waist and we will recommend a size. Unworn items can be returned free within 30 days.
THE FABRIC
Why merino wool
Merino wool moves sweat away from your skin as vapour and lets it evaporate from the fabric, so you stay dry and comfortable whether you are hiking, commuting or skiing.
Merino fibres naturally resist the bacteria that cause odour, so you can wear a base layer for several days, on the trail or while travelling, and it still smells fresh.
Wool can absorb up to 30% of its weight in moisture without feeling wet. In damp British weather it keeps insulating where cotton and polyester leave you cold.
Merino absorbs UV radiation: our lightweight layers offer UPF 25 and the midweight and heavyweight options UPF 50+, handy on long days in the hills.
Merino wool is naturally hard to ignite and self-extinguishes without melting onto the skin, unlike synthetic base layers.
Merino is a natural, renewable and biodegradable fibre. Sheep grow a new fleece every year, and a worn-out merino garment breaks down instead of shedding plastic microfibres.
FAQ
Men's merino base layer tops: FAQ
What is this 320gsm base layer top best for?
It is a heavyweight 320gsm merino layer, best for deep cold, winter camping and ski days. Compare every weight in our merino weight guide.
Which sizes are in stock?
Available to order now: , S, M, L, XL, XXL, XXXL. Our merino is true to size and designed to sit close to the skin; see the size guide for measurements.
Is this base layer top warm enough for skiing?
Yes. 320gsm heavyweight merino is our warmest weight, ideal under ski clothing in very cold resorts or if you feel the cold.
Which weight of merino base layer should I choose?
Pick by temperature and activity. 165gsm lightweight suits spring, summer and high-output sports; 190gsm is a year-round all-rounder; 250gsm midweight is the classic UK winter base layer for hillwalking, skiing and cold commutes; 320gsm heavyweight is for deep cold and standing still, such as fishing, stalking or winter camping. Compare them in our weight guide.
How should a merino base layer top fit?
Close to the skin without feeling tight, because a base layer can only move sweat away when it touches you. Our tops are true to size. If you are between sizes, size down for a next-to-skin layer under a jacket and size up to wear it on its own. Check the size guide.
Can I wear a merino long sleeve on its own?
Yes. The tops are cut clean enough to wear as a normal long sleeve T-shirt or turtleneck on cool days, then work as the first layer under a fleece or shell when it gets properly cold.
How many days can I wear a merino top before washing it?
Usually several days of normal wear. Merino resists the bacteria that cause odour, so airing it overnight is often enough on a trip. Wash it when it looks or feels grubby rather than after every wear.
Is merino warmer than a synthetic thermal top?
Merino feels warmer in real use because it keeps insulating when damp and regulates temperature, so you get less clammy on the way up and less chilled when you stop. Synthetic thermals dry faster but hold on to smells.
Here are actual measurements for a size Medium. I wish every garment company and reviewer would do this. I'll follow with my measurements and how it fits.Dimensions with top laid flat:Chest width: 20 inchesWidth at bottom: 19 inchesLength from center of neck at collar down shoulder to wrist: 36 inchesLength from armpit seam to wrist: 21.5 inchesLength from rear of collar to bottom: 29.5 inchesLength from from of collar to bottom: 24.25 inchesWidth at wrist opening: 4 inchesMy dimensions:Height: 5 feet 10 inchesNeck circumference: 13 inchesLength from center of neck at collar line down shoulder to wrist: 33 inchesLength from armpit to wrist: 18.5 inchesChest circumference: 38 inchesWaist circumference at naval: 31.5 inchesWaist circumference at hip bones: 32.5 inchesBicep circumference (not flexed): 11 inchesWrist circumference: 7 inchesI weigh 140 lbs.This top fits me slightly loose. It's not tight like a compression top, but still clings close enough to allow this to fit comfortably under another shirt. The material itself can stretch about 50%. For instance, the wrist width is 8 inches circumference unstretched, and 11.5 inches fully stretched.The garment is very soft and not itchy. I have eczema and this material is not irritating at all.I posted a photo of the washing instructions tag.
Here are actual measurements for a size Medium. I wish every garment company and reviewer would do this. I'll follow with my measurements and how it fits.Dimensions with top laid flat:Chest width: 20 inchesWidth at bottom: 19 inchesLength from center of neck at collar down shoulder to wrist: 36 inchesLength from armpit seam to wrist: 21.5 inchesLength from rear of collar to bottom: 29.5 inchesLength from from of collar to bottom: 24.25 inchesWidth at wrist opening: 4 inchesMy dimensions:Height: 5 feet 10 inchesNeck circumference: 13 inchesLength from center of neck at collar line down shoulder to wrist: 33 inchesLength from armpit to wrist: 18.5 inchesChest circumference: 38 inchesWaist circumference at naval: 31.5 inchesWaist circumference at hip bones: 32.5 inchesBicep circumference (not flexed): 11 inchesWrist circumference: 7 inchesI weigh 140 lbs.This top fits me slightly loose. It's not tight like a compression top, but still clings close enough to allow this to fit comfortably under another shirt. The material itself can stretch about 50%. For instance, the wrist width is 8 inches circumference unstretched, and 11.5 inches fully stretched.The garment is very soft and not itchy. I have eczema and this material is not irritating at all.I posted a photo of the washing instructions tag.
Comfortable a d very warm even for the thin one
Comfortable a d very warm even for the thin one
This 250g merino.tech top, sold by Merino US, is a thin, lightweight top, that I use as a base layer or would possibly use as a second layer, but only over another very tight fitting wool layer. I am a muscular and lean 5’9”, 175 lbs. My chest is on the small end of their medium sizing at 39”. This medium is form fitting, but loose compared to an athletic compression style top. For me, the neck is cut slightly lower than i am used to and the sleeves are a bit long, causing it to bunch up a bit along the length of the arm, but not enough to complain about it. I am just used to having a base layer be very tight fitting. My actual garment sleeve length measured 25 1/4" from the shoulder seam to the sleeve, which was spot on with one sizing chart, but different from a second sizing chart that advertises 24". The wool is soft and non-itchy. I stay warm while wearing the top by itself and especially when used under another layer/jacket. It breathes extremely well during moderate activity. I haven’t tested it yet under heavy exercise. I don’t really want it to shrink so I have only washed it on delicate/cold cycle and air dried, so I can’t speak on the long term durability, but wouldn’t recommend regular washer/dryer care, although they do claim a lifetime warranty. Their warranty statements are a bit confusing to me, as I read “lifetime warranty” and “110% Happiness Guaranteed Policy”, but also read “60 days for hassle-free refund, exchange, or replacement”. Perhaps I’m naïve, but I am overlooking the “60 days” statement and trust they’ll take care of it if I have a problem with the top in the future. I’d like to have several tops like this, but to me merino wool garments are very expensive. With that being said, their price is one of the lowest I’ve found. My order arrived in 2 days.
This 250g merino.tech top, sold by Merino US, is a thin, lightweight top, that I use as a base layer or would possibly use as a second layer, but only over another very tight fitting wool layer. I am a muscular and lean 5’9”, 175 lbs. My chest is on the small end of their medium sizing at 39”. This medium is form fitting, but loose compared to an athletic compression style top. For me, the neck is cut slightly lower than i am used to and the sleeves are a bit long, causing it to bunch up a bit along the length of the arm, but not enough to complain about it. I am just used to having a base layer be very tight fitting. My actual garment sleeve length measured 25 1/4" from the shoulder seam to the sleeve, which was spot on with one sizing chart, but different from a second sizing chart that advertises 24". The wool is soft and non-itchy. I stay warm while wearing the top by itself and especially when used under another layer/jacket. It breathes extremely well during moderate activity. I haven’t tested it yet under heavy exercise. I don’t really want it to shrink so I have only washed it on delicate/cold cycle and air dried, so I can’t speak on the long term durability, but wouldn’t recommend regular washer/dryer care, although they do claim a lifetime warranty. Their warranty statements are a bit confusing to me, as I read “lifetime warranty” and “110% Happiness Guaranteed Policy”, but also read “60 days for hassle-free refund, exchange, or replacement”. Perhaps I’m naïve, but I am overlooking the “60 days” statement and trust they’ll take care of it if I have a problem with the top in the future. I’d like to have several tops like this, but to me merino wool garments are very expensive. With that being said, their price is one of the lowest I’ve found. My order arrived in 2 days.
Good quality. Made in China.
I have purchased this heaviest weight shirt before from them. I have no way of measuring the advertised weight but the 2 I bought this week are thinner than ones I previously purchased. Nice shirt but disappointed in its weight
I have purchased this heaviest weight shirt before from them. I have no way of measuring the advertised weight but the 2 I bought this week are thinner than ones I previously purchased. Nice shirt but disappointed in its weight
The 320 is the best fitting top I've ever owned. The length is perfect, not too long not too short. The feel is incredible and so soft to the skin. And then to throw in a gift pair of high quality merino socks was icing on the cake. I've worn darn tough socks for years but your socks feel more comfortable, good job. This was the first time I ordered from you and tried to make another order 3 times but for some reason the transaction didn't go through. But I still believe you have an incredible product.
The 320 is the best fitting top I've ever owned. The length is perfect, not too long not too short. The feel is incredible and so soft to the skin. And then to throw in a gift pair of high quality merino socks was icing on the cake. I've worn darn tough socks for years but your socks feel more comfortable, good job. This was the first time I ordered from you and tried to make another order 3 times but for some reason the transaction didn't go through. But I still believe you have an incredible product.
Men's Merino Long Sleeve 320 Army Green
Men's Merino Long Sleeve [****]
Fits great! Perfect for the New England winters!
Fits great! Perfect for the New England winters!
Fit was fine. I am tall but slender and was hesitant about the small relative to sleeve length. The small landed on my wrist bone and fit well over the rest of me. I love these products and can wear them day and night, indoors or out.
Fit was fine. I am tall but slender and was hesitant about the small relative to sleeve length. The small landed on my wrist bone and fit well over the rest of me. I love these products and can wear them day and night, indoors or out.
Pleased with the fit. Have not worn them yet.
Pleased with the fit. Have not worn them yet.
This has become my new daily runner because of how warm it is!
This has become my new daily runner because of how warm it is!
Our son loved this Army Green color, and the fit is perfect! Switched to merino and will never wear anything else!
Our son loved this Army Green color, and the fit is perfect! Switched to merino and will never wear anything else!
Excellent tight fit! Very nice!
Excellent tight fit! Very nice!