Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
Pro Flex Thermal Baselayer Bottom: Heather Shadow from BN3TH Underwear
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Pro Flex Thermal Bottom

Heather Shadow

Mid-Weight Warmth. Ultra-Soft Cold Weather Comfort.

$70.00 CAD

Colour:
Size:

Size Guide



Designed for cold-weather performance, the Flex Thermal baselayer combines ultra-soft brushed fabric with high-stretch and moisture management to keep you warm, dry, and unrestricted. The Original 3D Patented Pouch supportive fit, and engineered construction, make it ideal for layering during winter adventures or everyday cold-weather comfort.

Fabric: 88% Recycled Polyester, 12% Spandex

The brushed recycled polyester interior provides soft warmth and moisture management, while spandex delivers high stretch, recovery, and support.

Waistband: 60% Polyester, 25% Recycled Polyester, 15% Spandex

Designed for secure hold without rolling or digging in.

SHORT FEATURES

The Original 3D Pouch
Mid-Level Warmth
Ultra-Soft Brushed Fabric
4-Way Stretch & Support
Moisture Wicking & Quick-Drying
Breathable
Gusset for Enhanced Mobility
Ionic+® Anti-Odour Technology
Premium No-Roll Waistband
Chafe-Free Flatlock Stitching

This baselayer bottom has a 27" inseam that can stretch to your body and a next-to-skin fit.

  • Machine wash cold
  • Do not bleach
  • Tumble dry low
  • Do not iron
  • Do not dry clean

View Size Guide

All BN3TH fabrics are soft and made from a performance stretch fabric. If your measurements are between sizes, select a larger size for a looser fit or a smaller size for a tighter fit.

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Free standard shipping is available on all orders above $75 (after discounts and before taxes).

All available shipping options will be visible at checkout. We ship orders within 1-2 business days, but this can increase during promotional periods.

Returns or exchanges will be processed up until January 31, 2026 for items purchased at a discount of less than 30% between November 8 and December 26, 2025. Products discounted by 31% or more will be final sale. For more information, check out our Frequently Asked Questions page.

Mid-Weight warmth, stretch, and support where it matters most. Built for cold weather layering.
MID LEVEL WARMTH
MID LEVEL WARMTH

Warmth

MOISTURE WICKING
MOISTURE WICKING

Stay Dry

IONIC+® ANTI-ODOUR
IONIC+® ANTI-ODOUR

No Stink

FLATLOCK STITICH
FLATLOCK STITICH

Chafe-Free

Features That Perform

THE ORIGINAL 3D PATENTED POUCH

The Original 3D Patented Pouch is engineered to lift, support, and separate, creating a natural space that eliminates friction and the need for constant adjustment. The result is a secure, comfortable fit that moves with your body all day.

INSEAM GUSSET

A gusset extends through the inseam to enhance mobility, reduce friction, creating an unrestricted fit.

BRUSHED WARMTH

Brushed 4-way stretch fabric creates a soft next-to-skin feel while helping trap warmth for comfortable cold-weather wear.

ENGINEERED COMFORT

WHY WE MADE THIS

We built this baselayer to do more than just keep you warm. We designed Pro Flex Thermal top and bottom to balance support, breathability, and freedom of movement, using brushed recycled fabric that feels soft against the skin and performs when your day picks up. It’s the layer you start with when the temperature drops.

SUSTAINABILITY MATTERS

Made with post-consumer recycled polyester fabric and elastic, this product is certified to the Global Recycled Standard (GRS).
OEKO-TEX® certified fabrics guarantee that our end products are tested and proven free from harmful toxic chemicals.