Headphone startup nura (HAX 08) recently closed a heavily oversubscribed series A at $21M—$6M more than anticipated thanks to enthusiastic support from investors. Led by existing investor Blackbird Ventures, the Series A was also backed by SOSV, AirTree Ventures, and Qualgro Investment. This funding round follows a $6M cash injection from Blackbird Ventures in 2017.

nura holds the title for highest VC raise to date for an Australian Kickstarter project, snagging $1.8M (the startup initially aimed to raise $200,000) from almost 8,000 investors in 2016.

The Melbourne-based company develops a personalized headphone called “Nuraphone,” which is tailored to each listener’s unique hearing profile. This allows the headphone to adjust sound to suit the user’s ears.

Speaking to SmartCompany on the key to nura’s robust investor support, CEO and co-founder Luke Campbell remarked: “We have very supportive investors…who could see our sales numbers which were also looking very good.”

He continued, “We were showing that we had excellent product-market fit, which made it easy to get investors on board. Startup founders should really focus on your product market fit. You’ve got to believe in your product and make it as good as you think it can be.”