BlackRock's iShares Bitcoin Trust (IBIT) attracted roughly $1.08 billion in net inflows over 20 days, with inflows recorded on seven days, according to on-chain data from Arkham Intelligence. Grayscale's Bitcoin Trust (GBTC) recorded approximately $254.7 million in outflows over the same period. IBIT's inflows included $454 million on Sept. 3 and $277.6 million on Aug. 27, lifting its holdings to about 785,000 BTC and assets under management above $60 billion. GBTC held roughly 130,000 BTC with about $10 billion in AUM. IBIT charges a 0.25% annual fee, compared with 1.5% for GBTC. U.S. spot Bitcoin ETFs collectively held more than 1.28 million BTC, or roughly 6% of Bitcoin's total supply, while the category attracted over $3 billion during the recent surge. The shift reflects IBIT's lower costs and BlackRock's access to financial advisers, wealth managers and institutional allocators. GBTC's outflows have continued through 2026 despite a broader market recovery, while Grayscale has promoted its lower-fee Bitcoin Mini Trust.