Allbirds is now selling socks.

The shoe brand that’s de rigueur for investors, entrepreneurs and aspirants in Silicon Valley has been bitten by the sock bug.

But, because this is Allbirds (and Silicon Valley), the company didn’t just launch a new line of socks. They’re using a “brand new material” called Trino that uses a yarn which includes Allbirds’ tree and wool blend.

The company is claiming that its new socks are made with natural ingredients and a combination of recycled plastic bottles and plant fibers and are 100% carbon neutral.

The socks are priced at $16 for tube socks, $12 for “no-show’ socks and $14 for quarter-length socks. There are six colors (a blue, grey, black, brown, pink and green option) and they’ll be available at stores in San Francisco, New York, Chicago, Boston and Seattle.

Allbirds isn’t the only company to sell sustainable socks. Osom makes its socks from up-cycled clothing materials and sells at a similar price point. Repreve, Zkano and Thought are also brands that use recycled materials to make their socks.

The shoe company has raised $77 million to date and is backed by investors including Lerer Hippeau, Tiger Global Management, Fidelity Management and T. Rowe Price.