The Finnish-American company Oura, which makes smart rings for sleep tracking, plans to raise up to 3 billion dollars on the American stock market as soon as next month. The company's valuation in that sale would exceed 16 billion dollars - according to Bloomberg. The firm has a little over 900 employees.

The jump is what deserves a second look. Last September Oura was valued at 10.9 billion in an 875 million dollar round, with Fidelity, ICONIQ and Whale Rock among the investors. In under a year, a paper valuation five billion higher. Nothing about the ring changed that much - what changed is the market's appetite.

Revenue, unlike the valuation, is real and growing fast: 500 million dollars in 2024, around a billion in 2025, and the company expects close to two billion in 2026. That is a rare figure in the wearables world, where most companies live off announcements. The real picture only emerges once the stock market filing becomes public - until then these are numbers the company reports about itself.

Competition arrived quickly. Samsung released its Galaxy Ring two years ago. But the most direct rival is Whoop, which transformed from a tool for elite athletes into something broader - it added hormone tracking and blood analysis, and reached a 10 billion valuation in March. Oura went through the same transformation, from a biohackers' toy into a sleep and recovery brand.

And here comes the part least mentioned in the press releases. Last week a class action was filed in San Francisco claiming Oura misleads buyers about the accuracy of its sleep measurement. The accusation is not that the ring fails to measure pulse or temperature, but that it claims to know the exact sleep stage - something that, according to the suit, requires electrodes on the scalp and sensors on the eyes, meaning a hospital laboratory.

The company responds that its reading of sleep stages has been validated in multiple studies against polysomnography, and that it will defend itself "in the appropriate legal forum". Note the careful formulation it adds: the Oura Ring "is not a medical device and is not a substitute for a clinical sleep study".

So the device is not medical, but the sale rests on how medical it sounds. That contradiction is not accidental - it is the entire business model of wearable electronics, and none of us reads the small print before slipping the ring on.

Who carries the risk if the sleep number is wrong? Not the company - that is already written into its response. The question is whether 16 billion dollars will still look reasonable once a court reads the same sentence.