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Underwear decoded: fabric, fit, and the numbers on the label — explained in plain language so you can pick with confidence.
Fabric guide — what each fiber actually does
Not all underwear fabrics feel the same. Here's the honest breakdown of the most common ones.
Cotton
Pros
- Naturally soft and gentle on skin
- Highly absorbent and breathable
- Hypoallergenic — easy on sensitive skin
Cons
- Low stretch, loses shape over time
- Slow to dry, clings when sweaty
- Can stiffen or shrink after many washes
Best for: Everyday casual and basics. Blend with 5%–10% spandex for stretch.
Modal
Pros
- Silky-soft with a smooth, fluid drape
- More absorbent than cotton, very breathable
- Holds color and shape through repeated washing
Cons
- Weak support, can slacken with wear
- Pricier than cotton
- Low wet strength — wash on a gentle cycle
Best for: Next-to-skin comfort pairs. Usually blended with cotton or spandex for durability.
Cotton + Modal
Pros
- Cotton's breathability plus modal's softness
- Smooth handfeel with better stretch
- More wash-durable than pure cotton
Cons
- Still some shrinkage risk
- Costs more than pure cotton
Best for: Mid-to-premium everyday pairs that balance comfort and structure.
Nylon
Pros
- High strength and abrasion resistance
- Lightweight, quick-drying — built for activity
- Slick, smooth handfeel
Cons
- Poor moisture absorption, can feel stuffy
- Generates static; weak against UV and ages faster
Best for: Outer layer of performance underwear. Pair with a cotton or modal inner layer.
Polyester
Pros
- Durable, wrinkle-resistant, holds its shape
- Dries fast
- Low cost and easy to dye
Cons
- Poor breathability, traps heat
- Pills easily, less comfortable against skin
- Carries environmental concerns
Best for: Blended trims for durability; budget lines or outerwear-style pairs.
Bamboo (bamboo viscose)
Pros
- Naturally antimicrobial
- Excellent wicking and breathability
- Biodegradable with a cool, light handfeel
Cons
- Lower fiber strength, wears faster
- Costs more
- Some bamboo-rayon processes raise eco questions
Best for: Sensitive skin and heavy sweaters; summer or eco-minded lines.
Spandex (also sold as Lycra)
Pros
- High stretch with strong recovery
- Adds hold, support and a secure fit
- Resists bagging, long-lasting
Cons
- Damaged by chlorine bleach and high heat
- Never used alone — always blended
- Cost rises with spandex content
Best for: A 5%–15% blend. Performance or slim-fit pairs needing firm support.
Decode the label — the numbers that matter
Fabric tags can look like code. Here's what each term means for your comfort.
Fabric composition
What the fiber actually is — cotton, modal, or synthetics — sets how soft and breathable it feels against your skin.
Tip: Look for a high share of natural or regenerated fibers.
Yarn count
How fine the yarn is. A higher count (e.g. 50s) means a smoother, lighter fabric.
Tip: Higher counts feel silkier next to skin.
Fabric weight (gsm)
Grams per square meter. Higher means thicker, sturdier cloth — 190 gsm outlasts 160 gsm and holds its shape better.
Tip: 180–200 gsm balances airflow and structure for daily wear.
Thread density (weave)
How many yarns pack into a given length. It drives how tight, dense and durable the fabric feels.
Tip: Denser weaves last longer but feel a touch firmer.
Spandex content
5%–15% gives stretch and snap-back. Too much traps heat and adds shine.
Tip: Active pairs can run higher; around 8% suits everyday wear.
Fit guide — pick the right cut
Four common cuts, what they're good at, and where they fall short.
Briefs
Pros
- Close, supportive fit
- Less inner-thigh chafe
- Lightweight and breezy
Cons
- Can dig into the thigh if too tight
- Less coverage, less of a secured feeling
Best for: Sports and tight outerwear.
Trunks
Pros
- Balanced support and freedom
- Versatile — rarely peeks out of pants
- Less inner-thigh rub
Cons
- Legs can ride up while walking
- Less support for high-impact moves
Best for: Daily commuting, jeans and chinos.
Boxer Briefs
Pros
- Full coverage and support
- High everyday comfort
- Stylish — works peeking under shorts
Cons
- Longer leg can restrict deep moves (squats, strides)
- Can feel bulky under dress pants
Best for: Desk jobs, lounging, colder months.
Boxers
Pros
- Maximum freedom, zero constriction
- Airy and breathable
- No visible outline through clothes
Cons
- Little support for the package
- Shows wrinkles under slim or dress pants
- Legs ride up and shift as you move
Best for: Home, sleep, hot weather.
Safety & care
How we keep every pair safe against your skin, and how to make them last.
- •OEKO-TEX Standard 100 — the global safety certification for textiles. Every GAGLI pair is tested for harmful substances, so it's safe against your skin.
- •Machine wash cold (below 40°C / 104°F), tumble dry low or line dry. Skip bleach and fabric softener — both break down spandex over time.
- •Waistbands and seams hold their shape through 50+ wash cycles, so a pair lasts well beyond a single season.
Go deeper — long reads
Three focused guides for shoppers who want the full picture.
Cotton vs Modal vs Synthetic
A side-by-side look at breathability, softness, durability, and price.
Read article3D Construction Explained
What '3D fit' actually means and why it matters for the crotch and thigh.
Read articleOEKO-TEX & Safety Certifications
How OEKO-TEX Standard 100 works and what it proves about your underwear.
Read articleReady to find your fit?
Browse the full lineup, or match your day to a style in our guides.