Fitbit said it had shipped one million of its Blaze wearables, unveiled at CES 2016 in January, with more than one million of its Alta devices also reaching the market since launch in March.

The company said that Blaze exceeded its own internal sales forecast, and topped the smartwatch and heart monitor categories on Amazon.

It also said that Alta has topped the fitness tracker and pedometer categories for the online retailer.

The success of the new products is important for Fitbit, with concern that the market leader could suffer as new players enter the market, and take-up of basic fitness trackers slows. Blaze, in particular, sees it moving further up the food chain, to battle health and fitness focused watches.

“The positive response we’ve received to Blaze and Alta demonstrates our continued ability to innovate and drive strong demand for Fitbit products, which is what has made and kept us the leader in the global wearables category,” said Woody Scal, chief business officer of Fitbit.