A once-niche upstart just beat out JPMorgan for the largest actively managed exchange-traded fund.

A record $275 million inflow on Thursday boosted the Ark Innovation ETF (ARKK) to just under $16 billion in total assets, according to data compiled by Bloomberg. That pushed the tech-heavy ARKK past the $15.2 billion JPMorgan Ultra-Short Income ETF (JPST).

Helmed by ARK Investment Management’s Cathie Wood, the fund hugely benefited from this year’s massive tech rebound from the March lows. Designed to invest in companies around the theme of disruptive innovation, it’s weighted heavily to biotech, internet and software companies. ARKK has risen 150% year-to-date, boosted in a big way by a 10% weighting to electric vehicle-marker Tesla Inc., which has surged 650% in 2020.

“ARK’s success has rocked the active world,” said Eric Balchunas, an ETF analyst at Bloomberg Intelligence. “These are stratospheric numbers for an active ETF strategy. But then again, so is her performance. The two are feeding off each other.”

ARKK’s rally ranks it as one of the top 10 performing U.S. ETFs this year in a universe of over 2,400 funds. It’s attracted roughly $7.6 billion worth of inflows so far in 2020, the bulk of which came in the second-half of this year as the tech sector took off.

Actively-managed ETFs in general have grown in popularity this year, adding $42 billion in 2020 compared to only $26 billion the year prior. Still, they make up less than 3% of total ETF assets in the U.S.

JPST, which tracks investment-grade securities maturing in a year or less, hadn’t held the crown long. It just surpassed the long-reigning PIMCO Enhanced Short Maturity Active ETF, ticker MINT, in September. But like many fixed-income funds, it’s suffered from record low interest rates, with its price remaining flat from its high at the end of July.

The new champ could face headwinds as a broad market rotation takes hold, raising the prospects for funds tracking companies set to benefit from a reopening economy. Amid tech’s selloff on Wednesday, ARKK declined 1.8%. But inflows are still strong, with the fund posting its biggest weekly gain in its history last week.

ARK’s success is a blow to newly launched active non-transparent ETFs, according to The ETF Store’s Nate Geraci. The new structures reveal their holdings only once a quarter, like a mutual fund, unlike traditional ETFs which do so daily.

“ARK Invest is essentially flaunting their holdings daily on social media and delivering significant outperformance while doing so,” said Geraci, the investment-advisory firm’s president. “ARK may single-handedly kill the non-transparent structure before it can walk because Cathie Wood is proving investment managers can generate outperformance with transparency.”

This article was provided by Bloomberg News.