Editor’s Note: This story originally published on May 4, 2018

CNN Business  — 

Allbirds co-founder Tim Brown came up with the idea for his shoe company after hanging up his soccer cleats.

Everything Brown had worn as a pro athlete in New Zealand, where he played for the All Whites, featured logos. He wanted something simpler, made out of natural materials. So he decided to make his own shoes out of wool.

“I got lots of pats on the head,” Brown said, describing the initial response. “I got told to leave that to people that know what they’re doing.”

Motivated by the skepticism, he set out to create a prototype and then launched a Kickstarter fundraising campaign. Within four days he’d raised $120,000.

Brown said he thinks the shoe has tapped into a “fundamental shift” in the way people work and play, a shift in tastes that the overall footwear industry hasn’t yet fully embraced.

After fulfilling the initial orders, Brown teamed up with Joey Zwillinger, who would become his co-founder and co-CEO.

“We took the next 30 days to get alignment,” Zwillinger told CNNMoney. “We did that by writing a pretty big business plan. It was like a 25, 30-page business plan. We really never shared it with anyone but it was about Tim and myself dialoguing and building a great partnership.”

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Their sneaker has been wildly popular, especially in the Bay Area, where the company is based. It’s even been called “the most comfortable shoe in the world.”

“I think when we realized that we blew through our first year business plan in a matter of two or three months that we were probably underselling ourselves when we started the business,” Zwillinger said.

Brown and Zwillinger said that they continue to take customer feedback on their products and modify the designs accordingly. They’re both very committed to making the best product they can, and the Allbirds sneaker has undergone 27 changes since launching in 2016.

They also have firsthand experience.

“No one tells you when you start a shoe company, but you have to wear that pair of shoes every single day,” Zwillinger joked.

The partners met through their wives, and that connection has upped the stakes.

“Whatever happened, we couldn’t jeopardize our wives’ friendship,” Brown said.

“That’s been tested at different times along the way, but I think we’ve done a really, really good job and I’m incredibly proud of the partnership I’ve built with Joey.”

The company’s first product is machine-washable wool sneakers, but Brown and Zwillinger describe Allbirds as a textile company that strives to be sustainable and create comfortable gear.

Allbirds has also debuted wool loafers and a line of kids’ sneakers with plans to unveil other products down the line.

That’s why they didn’t include “shoes” or “footwear” in their company name. The name Allbirds actually highlights what’s special about New Zealand, which is where its wool is sourced.

“It turns out that when man first settled in New Zealand in about 1200 – these are the Maoris that first came to New Zealand – there was all birds, no mammals,” Zwillinger said. “We thought it was just this really cool hearkening back to New Zealand before man had come. So ‘Allbirds.’”