The number of strategic beta exchange-traded funds on the market has grown substantially over the past few years, but these complex offerings aren’t always what they seem.

Asset managers have been eager to establish a foothold in this hot investment area, and advisors need to be mindful of what they’re buying, warned Patrick O’Shaughnessy, principal and portfolio manager at O’Shaughnessy Asset Management, speaking at the Morningstar Investment Conference in Chicago on Thursday.

“You need to ask, what is this strategy designed to do? Gather assets or produce real alpha, net of expenses,” said O’Shaughnessy. “That question is important. What is the motivation if, say, Goldman Sachs is launching a [fund]? Is it a land grab? That’s Wall Street. Be mindful of cost. Not all smart beta ETFs are bad. Some are good.”

Strategic beta strategies are designed to work over many years, rather than being a flavor-of-the-month investment. These strategies usually focus on investments using the factors of value, low volatility, quality and momentum.

However, with the interest in the theme high, some funds are claiming to be something they’re not, said Wes Gray, the founder, CEO and CIO of Alpha Architect.

He said sometimes there’s a significant difference between what a fund is called and what it actually does. For instance, Gray said, a value fund may say it’s based on the factor investing research of Eugene Fama and Kenneth French, yet there might be nothing in the portfolio construction showing it’s based on academic evidence.

Both Gray and O’Shaughnessy said such funds are chasing hot money, which is another reason advisors need to be careful. Short-term money isn’t going to be interested in something like value investing because not only does it mean buying unloved stocks, but also lagging the broader markets. And an investor who is chasing a hot investment doesn’t want to buy a fund that’s lagging.

In other words, O’Shaughnessy, holding value has to “hurt.”

A lot of ETFs creators who say their products are strategic beta are trying to promote the products as passive investments because they’re rules-based, but Gray said investors shouldn’t believe these are truly passive vehicles.

“The best point about factor investing is it is active investing,” he said. “To say it’s not is lying to yourself. So you need to do the same level of due diligence.”

The difference between true active management and strategic beta is that strategic beta is systematic and he thinks that gives it an upper hand.

“For me, personally, I like the benefit of a system,” Gray said. “It pulls the human element out. It helps the buyer know what they’re buying. … If I know the process and the model, I have confidence in what they’re buying.”

Another reason to look closely at these funds is to make sure that their systems will be different from, say, the Standard & Poor’s 500. New factor investing funds are starting to include more than one factor—blending the value and momentum factors, for instance.

“If you do factor investing, don’t accidently buy all the factors and recreate the S&P,” Gray said. “Know what you’re buying.”

O’Shaughnessy agreed that the concentration is important when you’re taking an integrated approach.

“If you want to focus on multiple things, make sure the net portfolio is still very different from the market. That’s the biggest pitfall you want to avoid,” he said.