Shares in the wearable technology company Fitbit have soared nearly 50% on their first day of trading on the New York Stock Exchange.
Initially priced at $20 a share, they closed at $29.68.
The company, which makes wristbands that track your calories and footsteps, raised $732m (£460m) from the share sale.
Fitbit plans to use the money raised for research and development and possible acquisitions.
Unlike many technology companies to list, the company is already profitable, making $131.8m in net income in 2014 with sales of 10.9 million devices last year.
Fitbit's Woody Scal told the BBC that the company was just at the beginning of its journey.
"There's tremendous innovation ahead in hardware and in what sensors can say about what the body is doing," said Mr Scal.
"And then it's about taking that information and helping motivate people. The next step is guiding them to what they can do with that information."
It is currently the market leader in the industry, according to the research firm IDC.
However IDC, and others, warn that it faces stiff competition in the the form of Apple's newly-launched watch, as well as from Chinese smartphone maker Xiaomi, which makes the Mi-Band.
"Demand from emerging markets is on the rise and vendors are eager to meet these new opportunities," said Ramon Llamas from IDC in a research note.
"What remains to be seen is how Apple's arrival will change the landscape," he added.
"The Apple Watch will likely become the device that other wearables will be measured against, fairly or not. This will force the competition to up their game in order to stay on the leading edge of the market."
Julie Ask, mobile analyst at Forrester believes that Fitbit still needs to work out a way of generating sustainable revenue from services connected to its devices.
"This battle will be won or lost by the company that can provide services that motivates the consumer to change their behaviour. It's not just the hardware that counts," she said.
Fitbit is also facing two lawsuits from its rival Jawbone, which accuse Fitbit of stealing data and patents. It denies the accusations.