Bamboo Motion Boxer Brief-Socks & Underwear-Free Fly-Heather Black-Mountain Sports
Free Fly

Bamboo Motion Boxer Brief

Buttery-soft bamboo comfort that moves with you

$32
Color: Black
Size:
Size guide
  • Free shipping on orders $150+
  • Free pickup at our Arlington, TX store today
  • Free 30-day returns
Top features
Buttery-Soft Bamboo Viscose
4-Way Stretch
Quick-Dry Performance
Description

The Mens Bamboo Motion Boxer Brief is Free Fly's take on a piece you'll reach for again and again — built on the bamboo-based fabric they're known for, with a fit and feel tuned for life lived outside.

Built with bamboo-based and recycled fibers, because the gear that takes you outside shouldn't take more from the planet than it has to.

Perfect for
Everyday
All-day comfort.
Travel
Flights & road trips.
Workouts
Hot-day training.
Features
  • Buttery-Soft Bamboo Viscose. Free Fly's signature viscose-from-bamboo blend has a smooth, buttery handfeel that's softer than your standard tee — comfort you notice the second you put it on.
  • 4-Way Stretch. Stretch built into every direction gives you total freedom of movement, then recovers its shape wash after wash.
  • Quick-Dry Performance. Lightning-fast dry times mean sweat, surf, or a sink-wash on the road won't slow you down.
  • Flat Seams & Plush Waistband. Flat seams won't dig in, and the plush elastic waistband moves with you — no ride-up, no chafe.
Materials
  • Fabric: 68% Viscose from Bamboo / 29% Polyester / 3% Spandex (Ultra-soft, stretch knit). Made by Free Fly.
About the brand

Free Fly started with a love of the water and a mission to make natural, breathable clothing that keeps up. Their bamboo-based fabrics are buttery soft and built for comfort from sunrise paddle to sunset hang. At Mountain Sports, we love Free Fly because it’s made for life lived outside — easygoing, effortless, and always adventure-ready.

Shop all Free Fly

SKU BBB300-S · Style BBB
Size guide

Free Fly Size Chart - Men's Apparel

Free Fly Sizing Chart

All measurements are in inches and reflect body measurements. If you are in between sizes, size up for comfort.

Men's Size Guide (Men's Apparel - single chart for tops and bottoms):

Alpha Sizes Numeric Sizes Chest Waist Hip Sleeve
S 30–31 36–38 30–32 34–37 32–33
M 32–33 38–40 32–34 37–39 33–34
L 34–35 41–43 35–37 40–42 34–35
XL 36–38 44–46 38–40 43–45 35–36
XXL 40 47–49 41–43 46–48 36–37
3XL 50–52 44–46 49–51 36–37

Numeric Sizes are waist equivalents. How to measure: Chest - circumference at the widest part of the chest, about 1" down from armpit; Sleeve - with arm slightly bent, from center back neck to shoulder, down arm to wrist bone; True Waist - around the natural waist, narrowest part of the torso; Hip - around the fullest part of the hips. Inseam length is listed on each product page.
Performance

How it ranks across conditions.

Calibrated against comparable products we stock, so you can compare like for like.

Softness

Standard
Soft
Buttery-soft

Free Fly's signature buttery handfeel

Breathability

Low
Moderate
High

Light, airy fabric

Sun protection

Not rated
UPF 20–30
UPF 50+

Rated UPF 50+

Best for

Is this right for you?

Hot, active days

Quick-dry, 4-way stretch knit with flat seams that won't dig in.

Not for: Want a compression-style brief for racing. Shop all Free Fly

Travel

Lightweight and quick-drying — rinse in the sink, dry overnight.

Not for: Want the same bamboo softness up top too. Try the Bamboo Flex Pocket Tee

Full spec sheet

Technical Specs

Fabric68% viscose from bamboo / 29% polyester / 3% spandex
Fabric weight180 GSM
Sun protectionUPF 50+
Stretch4-way stretch
FitRelaxed through the body
SizesSM–2XL
CareMachine wash cold with like colors, tumble dry low
Questions, answered

Before you buy.

Pulled from chats, emails and store visits. The things people actually ask us before they buy. Don't see yours?

Ask a question
How do I wash bamboo viscose?

Machine wash cold on a gentle cycle with like colors, then tumble dry low or hang dry. Skip bleach and fabric softener — they break down bamboo viscose fibers — and avoid high heat, which can affect the soft handfeel.

Do these ride up or chafe?

They're built not to: flat seams won't dig in, 4-way stretch moves with you, and the articulated front pouch and plush elastic waistband keep everything comfortably in place.

How does Free Fly sizing run?

Free Fly tops generally run true to size with an easygoing, classic fit. If you're between sizes, size up for a more relaxed look or down for a trimmer fit — and check the size guide on this page for exact measurements.

Real people, always

Our story

Someone who's been there

Ask about a trail, a tent or a fit, and a person who uses the gear writes back.

Picked, not just stocked

We carry the brands we trust on our own weekends outside.

Easy if it's not right

Free 30-day returns, and help finding the one that is.

Free shipping over $150

Shipped nationwide since '96. Some exclusions apply.