Every PUFFIT jacket begins with the same question: how can we protect women from rain without making them feel like they are wearing outdoor gear? The answer is STM-TEX™, our engineered waterproof fabric technology. It is the foundation of our rainwear collection, and it was developed specifically for the way modern women actually live: walking, commuting, travelling, socialising, and navigating weather that rarely stays the same for more than an hour.

This article explains what STM-TEX™ is, how it works, and why it matters when you are choosing your next waterproof jacket.

What Is STM-TEX™?

STM-TEX™ is a multi-layer waterproof fabric system developed by PUFFIT. The name stands for our core philosophy: Stay Dry. Move Freely. It combines a protective outer face, a waterproof-breathable membrane, and a comfortable inner layer into a single textile that performs in wet conditions while feeling good against the skin.

Unlike simple coated fabrics, which can feel stiff and trap sweat, STM-TEX™ uses a membrane-based construction. This means the fabric is not just treated to repel water; it is engineered with microscopic physical properties that actively manage moisture in both directions.

How Waterproof Fabric Technology Works

To understand STM-TEX™, it helps to understand the difference between waterproofing technologies.

Coated Fabrics

The most affordable waterproof jackets use a polyurethane coating applied to the inside of the fabric. This coating creates a solid barrier that water cannot pass through. The downside is that it also blocks air and moisture vapour. Over time, coated fabrics can become stiff, noisy, and less breathable. They are fine for occasional emergency use but uncomfortable for all-day wear.

Membrane Fabrics

Membrane-based fabrics contain a thin layer with billions of microscopic pores. These pores are roughly 20,000 times smaller than a drop of water, so liquid rain cannot pass through. However, they are 700 times larger than a molecule of water vapour, which means sweat and body heat can escape.

This dual behaviour is what makes high-quality waterproof fabric technology so effective. You stay dry from the outside without becoming damp from the inside.

STM-TEX™ Construction

STM-TEX™ uses a membrane-based construction combined with a durable outer fabric and a soft inner layer. The result is a textile that:

• Blocks wind and rain
• Breathes during movement
• Resists daily abrasion
• Maintains a soft, wearable drape
• Works as part of a fashion silhouette, not just a technical shell

Key Performance Benefits of STM-TEX™

Reliable Waterproof Protection

STM-TEX™ is tested to withstand sustained rainfall, making it suitable for everything from sudden summer showers to long autumn downpours. The membrane sits at the centre of the fabric, protected by the outer layer, so it is less likely to be damaged by dirt, oil, or repeated flexing.

Breathable Comfort

One of the most common complaints about rain jackets is that they feel like portable saunas. STM-TEX™ addresses this by allowing water vapour to escape. Whether you are rushing to catch a train, walking uphill, or carrying shopping, the fabric helps regulate your temperature so you do not arrive damp and uncomfortable.

Wind Resistance

The same membrane that blocks rain also blocks wind. This makes STM-TEX™ jackets ideal for breezy coastal towns, exposed city streets, and open parks. You can wear them as an outer layer even when it is not actively raining.

Lightweight and Flexible

Despite its protective performance, STM-TEX™ remains light and flexible. The fabric drapes softly rather than standing away from the body, which is why PUFFIT jackets can be cut in oversized, fashion-forward shapes without looking bulky.

From Fabric to Finished Jacket

Great fabric alone does not make a great jacket. At PUFFIT, we pair STM-TEX™ with construction details that protect every entry point:

• Fully taped seams: Every stitched seam is sealed with waterproof tape so rain cannot leak through the needle holes.
• Waterproof zips: Exposed zips are coated or covered to prevent water ingress.
• Adjustable hoods: Wide-brim designs channel rain away from the face and stay in place during gusts.
• Sealed cuffs and hems: Adjustable closures keep wind and rain from sneaking in at the wrists and waist.
• Protected pockets: Pockets are positioned and finished so your phone, keys, and travel card stay dry.

These details turn a waterproof fabric into a waterproof system.

STM-TEX™ vs. Ordinary Waterproof Materials

Caring for STM-TEX™

Like all performance fabrics, STM-TEX™ benefits from proper care. Dirt and body oils can reduce the effectiveness of the durable water-repellent finish over time, which is the treatment that makes water bead up on the surface.

To keep your STM-TEX™ jacket performing at its best:

• Wash at 30°C on a gentle cycle.
• Use a specialist technical wash or a small amount of mild liquid detergent.
• Avoid fabric softener, bleach, and powder detergents when possible.
• Rinse thoroughly.
• Air dry or tumble dry on low if the care label allows.
• Reapply a wash-in or spray-on DWR treatment if water stops beading.

With the right care, an STM-TEX™ jacket will keep performing season after season.

Why We Built It

PUFFIT exists because we were tired of choosing between practical rainwear and clothes we actually wanted to wear. We started in London, where rain is less an event and more a background condition, and we wanted outerwear that could handle that reality without sacrificing style.

STM-TEX™ is the result of that intention. It is waterproof fabric technology, but it is also a belief: that protection, comfort, and design can exist in the same garment. Whether you are walking to work, travelling for the weekend, or heading out with friends, your jacket should keep you dry and help you feel like yourself.

Find Your STM-TEX™ Jacket

STM-TEX™ is used across the PUFFIT rain jacket collection, from our cropped oversized silhouettes to our longer parka styles. Each jacket combines the same protective technology with different shapes, lengths, and features so you can choose the one that fits your life.

If you want to understand more about how waterproof jackets are rated and what to look for when buying, read our complete guide: What Makes a Great Waterproof Jacket?

Frequently Asked Questions