Behind the Design: Kollen by Tiril Eckhoff

When Olympic champion Tiril Eckhoff first visited Kastel HQ and met our designer Andreas, she told him something that stuck:

“I love the Stryn boots — they’re warm, waterproof, and give me good grip. But when I’m really out in the elements, I need even more.”

That was all Andreas needed to hear.

He’d already been exploring something new behind the scenes: modular shoes. The idea? Instead of buying a whole new pair, you could change and upgrade parts of the shoe to adapt to different conditions. More comfort. More warmth. Less waste.

And Kollen was the perfect project to bring that idea to life...

First Step: More Protection

Andreas started by looking at how to protect your feet even better than Stryn.

• He extended the mudguard higher up the shoe, to block slush and water where it really matters.

• Then came the modular shaft — a high-padded collar that attaches securely to the shoe. It works like a jacket for your feet, shielding your ankles and keeping snow out when winter really kicks in.

Enter: The Velcro Phase

Andreas has a soft spot for technical details. He dove into velcro research — and yes, velcro is used on the International Space Station to keep things in place. If it works in space, it works for a winter boot. The shaft attaches easily and holds tight — without zippers, buttons, or snaps that fail when it’s freezing.

On in Seconds

Most winter boots are a hassle: you untie, unzip, tug, and stomp. But we all know that real life doesn’t wait, so Kollen uses elastic laces. You just unzip the shaft and slide your foot in. Done.

Want More Warmth? Upgrade It

Not everyone needs the same level of warmth. So instead of overbuilding the boot, we leaned into the modular idea. You can upgrade the shaft to a version lined in Norwegian wool — perfect for colder days and deeper snow. Snap it on, and just like that: a warmer boot.

What’s Next?

Now that we’ve launched our first modular winter boot, we’re thinking even further.

New shafts in new materials? Charms or color patches to customize your look? More upgrades instead of more boots?

We’re already testing the next step. But first — get your Kollen on. Wear them. Love them. And next year? Maybe you don’t need new winter shoes. Just a new shaft.