Trunk Size Chart

Fit Profile: True to Size

Size: S M L XL XXL
Waist: 28-30" 31-34" 35-39" 40-43" 43-46"
Outseam: 6-7" 7-8" 8-10" 10-11" 11.5"

  *Standard Trunk Size Guide Measurements:

Waist: Circumference measurement of waist. Trunks are designed to fit above the hips.

OutseamMeasure the length from the intersection of the waistband & hip to the bottom hem, follow the outer seam.

*Product measurements can vary by 1/2" 

Your purchase includes our "Love Your Fit" guarantee

If you don't love the fit, send it back and we'll exchange the size so you're happy.

 

Flex Trunk

125

Flex Trunk

125

Designed with increased compression, breathability, and support for your more intense days. Learn More

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Maroon Red
Black
Gray
Green
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Size Guide

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Flex Trunk

Signature 40° Side-Fly • Anti-Odor • Temperature Control • 84% Polyester • 16% Spandex


"Lightweight, comfortable, and durable. I can wear the Flex Trunk anywhere with confidence that they will perform!"




  • You deserve better boxers


      • Cool Where it Counts

    84% Polyester and 16% Spandex, our mesh zones are strategically placed to remove heat and keep you cool when and where it matters most.

      • Side Fly Innovation

    BYLT's signature 40° side-fly offers a more comfortable draw and easier access. It's time you see how we changed men's boxers for the better.

      • No Roll. No Marks.

    The Flex Trunk's no-roll waistband fits comfortably while leaving you mark free after a long day. Say goodbye to boxers that roll and ride up.




    Men's Temperature Control Flex Trunk Underwear Pack by BYLT Basics.



 

Customer Reviews

4.8 Based on 125 reviews
5 Star
82% 
102
4 Star
16% 
20
3 Star
2% 
2
2 Star
0% 
0
1 Star
0% 
1
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06/29/2019

Flex Boxer Brief

Joseph A.

Very comfortable throughout the day. Worth the price and will definitely buy more boxers.

06/26/2019

Great product good customer service

Erich H.

Good fitting great looking underwear.

06/25/2019

Amazing Undies

Joseph F.

Great for the gym and the streets, and they look super cool, too!

06/25/2019

Great pair of underwear

Vince T.

Great for working out.

06/21/2019

Tried these briefs and...

Russ W.

I LOVED THEM! I wore them at the gym and in the ocean under swim shorts. Loved them!

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Our Signature Fabrics

BYLT Blend™ Fabric

Premium signature blend of Cotton, Polyester, and Spandex. Perfect for your essential everyday shirt, leaving you with that flawless BYLT Fit.

LUX Blend™ Fabric

High-quality performance blend of Cotton, Polyester, and Spandex. Reactive fabric allows for slight reduction in length to provide the perfect structured fit.

Close
Trunk Size Chart

Fit Profile: True to Size

Size: S M L XL XXL
Waist: 28-30" 31-34" 35-39" 40-43" 43-46"
Outseam: 6-7" 7-8" 8-10" 10-11" 11.5"

  *Standard Trunk Size Guide Measurements:

Waist: Circumference measurement of waist. Trunks are designed to fit above the hips.

OutseamMeasure the length from the intersection of the waistband & hip to the bottom hem, follow the outer seam.

*Product measurements can vary by 1/2" 

Your purchase includes our "Love Your Fit" guarantee

If you don't love the fit, send it back and we'll exchange the size so you're happy.