EXCLUSIVE –Betterment, the online financial adviser, today launched a new feature that lets its retail customers further customize their asset-class investment.

The feature is an extension of Betterment’s core growth strategy – personalization, Betterment CEO Jon Stein told Bank Innovation.

“This is a significant step down the strategy of letting users personalize the way they use Betterment,” Stein said. “We realized the value of personalization when we first launched muni-bonds and taxable bonds and then added smart beta portfolios and socially responsible portfolios.”

Today’s feature, called Flexible Portfolios, is different in that it allows the investor to control the investment distribution within the asset-class portfolio.

Typically, when signing up for Betterment, a user can personalize his portfolio (combination of stocks and bonds) around a goal, or a type of portfolio like socially responsible ETFs, Stein explained. With this new feature, users get a higher level of control of their asset class by being able to choose not just the amount allocated to each asset class, but also the asset class itself.

Of course, this feature seems like one that requires a certain level of knowledge on the investors’ part, that’s why Betterment has opened this feature to only investors with than $100,000 in investments.

The feature also runs the danger of causing the user to make poor allocation choices, a possibility Stein is aware could easily happen.

“So, to tackle that we put in place an alert system,” he said. “Investors are sent alerts on the overall risks of their choices and things like poor diversification issues, etc. We also provide them guidance on how they should be investing to reach their goal based on timeframe and expected returns.”

“This feature makes us the first online financial advisor to do so at the cost we’re offering,” Stein said. That cost is zero dollars, he said.

In fact, Stein prides his company in offering services at a reasonable rate without using money making tactics that many of its peers are notorious for (Don’t know what we’re talking about? Read this Wired Article).

“We always have no incentive for the fund recommendations we make,” Stein said. “We are an advisor and we are paid no fees. We are indifferent to the funds that our clients choose.”

“What others [like Vanguard, Schwab or Wealthfront] do, I would never do that,” he said.

Stein is referring to the fact that customers of these institutions have to proactively choose to opt out of funds that these advisers are tied to.

That’s one of Betterment’s distinguishing qualities, Stein said, along with its personalization mantra. Indeed, it seems to be working. Since its launch in 2010, Betterment has seen impressive growth. “Every year we’ve seen faster growth than the last year,” he said.

Currently, it has 340K customers and $13.5 billion dollars under management. By the end of 2016, it had about 210K users and $6 billion in assets under management.