Spot bitcoin and ether ETFs collectively lost more than $520 million in a Wednesday session as higher Treasury yields reduced the appeal of risk assets. BlackRock's iShares Bitcoin Trust, or IBIT, recorded approximately $144 million in net outflows, following $161.7 million in redemptions during the previous session. Fidelity's FBTC led that earlier selloff with $214.8 million in outflows, while Bitwise's BITB, ARK 21Shares' ARKB and Grayscale's GBTC also recorded smaller outflows. U.S. spot bitcoin ETFs alone saw approximately $450.4 million leave on Sept. 15, the largest single-day redemption since June, according to researchers. Earlier in September, the same group of funds attracted $731 million in one day. Cumulative September flows through mid-month remained modestly positive at about $17 million, reflecting a near balance between inflow and outflow sessions. Despite the withdrawals, IBIT remains the largest bitcoin ETF by a wide margin, with approximately $59 billion to $60 billion in net assets, and added more than $1 billion in bitcoin holdings during a recent 20-day accumulation period. U.S. spot bitcoin ETFs have attracted approximately $55 billion in cumulative net inflows since launching in January 2024, after years of regulatory resistance from the SEC (U.S. securities regulator). Their approval expanded traditional finance's access to Bitcoin price exposure, while the newer and smaller ether ETF market added to Wednesday's outflows.