While Friday's entry ends GBTC's streak of net withdrawals, BlackRock's iShares Bitcoin Trust (IBIT) is challenging the fund for the title of largest bitcoin ETF. GBTC now has $18.1 billion in assets, versus the IBIT $16.9 billion. The IBIT, now in second place, started at zero in January, while the GBTC had more than $26 billion.