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Runterra Bio Tee

W's Runterra Bio Tee

Heads up, this gear will ship in 3-5 weeks. Learn more about pre-orders.


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run everywhere guarantee
free shipping over $50
free 60 day exchanges
Gabby is 5'8" and wears size S Regular fit , Size Chart

Run in it, sweat in it, live in it — then biodegrade it!

The first synthetic-blend running shirt that biodegrades like a 100% cotton tee, our Runterra Bio offers the enhanced moisture and odor control of specially-formulated 37.5® polyester with the comfort and versatility of cotton. This new, innovative fabric breaks down into organic compounds in under four years. Conventional polyester takes four hundred.

Don’t sweat it this tee will only start to biodegrade in anaerobic (oxygen-poor) environments. It breaks down in the landfill, not in your closet.

Explore more

Volcanically-enhanced comfort

Microscopic volcanic ash embedded into the fabric boost thermal, vapor + odor regulation to maintain body comfort during activity

Hang it up

An elastic locker loop is integrated into the back neck tape for easy hanging



Runterra Bio is powered by a specially formulated 37.5® polyester with enhanced biodegradation to break down into bio-based compounds in under 4 years in an oxygen-poor environment like a landfill

Premium cotton
Made from long staple, US-grown Supima® cotton for superior softness, strength + durability

Everyday looks
Easy to wear, casual cut with a slightly rounded back hemline

Active comfort
Blended with 37.5® polyester, a special technology utilizing the natural benefits of microscopic volcanic ash to provide enhanced thermal, vapor + odor regulation to maintain body comfort during activity

Wear more, wash less
The natural odor resistance of cotton is boosted by the volcanic particles which "trap" odors so you can put this top through repeated wear

Ergonomic comfort
Shoulder seams are rolled back off the top of the shoulders for ergonomic comfort

Hang it up
An elastic locker loop is integrated into the back neck tape for easy hanging

Shrinkage is natural
This top is made from 70% natural fibers and is not pre-shrunk so some shrinkage may occur, up to half a size

materials + specs

70% Supima® cotton, 30% 37.5® tech polyester

Garment made in Vietnam

86g / 3oz (W’s Small)

Fabric Callout


Lightweight, resilient, and versatile, Runterra wears like your softest cotton tee with the added benefits of active odor-resistance and thermoregulation — thanks to volcanic particles embedded within the fabric.


care instructions

Wash cold with like colors

Machine dry low or hang dry for best results and lifespan of the garment

Heads up — Runterra is not pre-shrunk

We have relaxed the body and slightly lengthened the sleeves of this top to accommodate for some shrinkage which may occur in the wash cycle since Runterra is made from a majority natural fiber.

Avoid washing and drying with high heat.


Why do biodegradable synthetics matter? 

While we design Janji gear to last and hold up to the demand of years of running, no tee or running shorts should last forever. With this in mind, we are researching innovative ways to improve end-of-life cycle management of our apparel. While we look into longer-term solutions and circular methods — recycle, repurpose and reuse programs — we also know that most textiles are thrown out and end up in landfills. Conventional synthetics, used heavily in active apparel for their high-performance functionality, do not biodegrade in typical landfill conditions. This includes synthetics made from recycled materials, and is why most plastic seemingly lasts forever.

We are seeking solutions to fix this as a performance apparel company that relies on synthetics, including the use of non-ecotoxic biodegradability within our textiles like this new Runterra Bio. This is the first step on a better path forward.

Runterra is made from premium, long-staple Supima® cotton which is 50% longer and up to 45% stronger than other cottons (and softer, too). The stronger the fiber, the more durable the garment, and therefore the more it can be worn. Supima® cotton is grown by a select few family farms that utilize advanced water and soil management techniques to reduce consumption and ensure the health of the land for optimal renewability.

Runterra fabric is also OEKO-TEX® certified, meaning it is free from harmful chemicals and is fabricated in a way that meets a high environmental standard.

Learn more about our sustainable initiatives here.


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Customer Reviews

Based on 10 reviews
Katja Hebestreit
Wear it for: Running, Hiking, Camping, Climbing, Mountain Biking
Product Fit: Spot-on
Height: 5'4" to 5'6"
Usual Size: S
Size Purchased: S
My absolute favorite running shirt!

I love the loose fit and non-plastic feel of this shirt.

Wear it for: Running
Product Fit: Spot-on
Height: 5'4" to 5'6"
Usual Size: S
Size Purchased: S
Super comfy! Best Running gear!

Super comfy! Best Running gear!

Kimberley Gilman
Wear it for: Hiking
Product Fit: Spot-on
Height: 5'0" or shorter
Usual Size: XS
Size Purchased: XS
A great all purpose tee

This was my 2nd W's Runterra Bio Tee. I love it and am extremely happy with my purchase. I just wish there were more colors to choose from as I would buy more!

Rosa M

I love this tee! It's perfect for everything. It's light, it's breathable, it doesn't smell, and the colors are fun!

Nice Tshirt

Super soft, comfortable fabric. Fun design, and representative of a great cause. I really like this shirt!

Great shirt

Super comfy! I don't normally like cotton/cotton blend shirts when I'm active since I sweat a LOT, but this one does a good job keeping me cool and doesn't have that super clingy cotton shirt feel when it's wet.

Alex Perry
Love This Shirt

This is the first Runterra shirt I've owned, and I love it. It's lightweight and good for both backpacking and hiking. It also is really good at odor control. I took this on a six mile hike, sweated (as we do), and then took it out for a run the next day. Still smelled fresh.

Love the material

Very soft and comfy material. Really love this shirt for everything! I usually stay away from cotton or cotton blends when running, but this keeps me cool and still wicks away sweat.

Marie Moore

W's Runterra SS Tee

Great casual t-shirt

I haven’t tried this shirt for running, but I love it for an every-day casual tee. Pairs great with the transit tech shorts or groundwork tights. I really like the colors this season