Wearable technology company Fitbit saw its revenue beat expectations and more than triple to $400m (£256m) in the second quarter of the year.
Margins fell, however, due to higher spending on new products.
Net income rose to $17.7m in the quarter from $14.8m in the same period the previous year.
It is the first report as a public company for the makers of wristbands and devices that track heart rate, calories, steps and sleep pattern.
The company had gone public in June and stocks had risen nearly 160% since its debut.
The declining gross margins overshadowed the strong revenue and shares fell by more than 15% in Thursday’s after-hour trading.
The company said adjusted margins fell to 47% in the three months ending June 30, down from 52% the previous year.
Fitbit said it does not expect margins to improve for the rest of the year.
The firm said it sold 4.5 million devices in the second quarter.
Revenue rose to $400m from $113m in the same period the previous year.
The gains were due to expansion to Asia and Europe and strong general demand for its devices.
For the next quarter, the company said it expects revenue to be slightly lower, in the range of $335m to $365m.