A former relic of the mutual fund industry is about to become exchange traded.

Fidelity filed last week to launch ETF versions of some of its mutual funds including the legendary Fidelity Magellan Fund. Once run by famed investor Peter Lynch, the Fidelity Magellan Fund was the best-performing mutual fund in the world from 1977 to 1990, raking in staggering 29% annualized returns.

That outperformance has since faded, however, and the Magellan fund’s 77-basis-point ownership fees have cannibalized its gains.

The fund has underperformed the S&P 500 significantly over the last 20 years, down 11% while the S&P is up more than 134%.

Now, the fund will enter the ETF sphere in an actively managed, nontransparent format. Unlike standard ETFs, so-called ANTs disclose their holdings quarterly instead of daily in an effort to prevent managers from getting front-run on their strategies.

“This fund’s been out there for 57 years and it’s definitely not the fund that it was when Peter Lynch was running it,” Kim Arthur, president and CEO of Main Management, told CNBC’s “ETF Edge” on Monday.

“It’s underperformed its benchmarks and … probably most of the underperformance is from the 77-basis-point fee that it charges,” he said.

While the ETF structure largely offers investors lower costs and higher tax efficiency than the mutual fund format, there’s not much else to be excited about in this transition, Arthur said.

“If they were to come out and say, ‘Hey, we’re reconstituting this and we are now going to be a thematic innovation strategy — not just growth, but we’re focusing in on where the puck’s going on innovation, on great themes,’ then you could maybe say, ‘We’re going to go ahead and give this thing a second derivative life,'” he said. 

“But to just go ahead and change the wrapper