iShares U.S. Aggregate Bond Index Fund
U.S. stock index fund · tracks Bloomberg U.S. Aggregate Bond Index
As of its 2026 Q2 report, iShares U.S. Aggregate Bond Index Fund held 1 positions with $3.27B in net assets. Its ten largest holdings made up 100.3% of the fund. The WFBIX share class costs 0.05% a year. Over the 12 months to May 2026, WFBIX returned 5.1%, with dividends reinvested.
The investment objective of iShares U.S. Aggregate Bond Index Fund (the Fund ), a series of BlackRock Funds III (the Trust), is to seek to provide investment results that correspond to the total return performance of fixed-income securities in the aggregate, as represented by the Bloomberg U.S. Aggregate Bond Index (the Bloomberg U.S. Aggregate Index or the Underlying Index ).
The fund seeks to match the total return of the Bloomberg U.S. Aggregate Bond Index by investing in a representative sample of the approximately 14,006 investment-grade fixed-income securities in the index, including government bonds, corporate bonds, mortgage-backed securities, and asset-backed securities, with securities selected according to their relative weight in the index and characteristics such as credit quality, sector, and maturity. Because the fund invests in a representative sample rather than all index constituents, its returns may diverge from the index. The fund is structured as a feeder that invests all assets in a master portfolio.
What you own
| Company | Weight | Value | Shares | Reported price |
|---|---|---|---|---|
MASTER INVESTMENT PORTFOLIO | 100.25% | $3.28B | 360.8M | $9.09 |
Reported price is the fund's own reported value divided by its own reported shares at 2026-06-30 — not a live quote, and not what the fund paid.
All 1 holdings, with the share counts as filed, open with a free account.
What the fund is made of
Percentages are of fund net assets. Rounding, liabilities and short positions can make totals differ from 100%.
| Stocks | 100.25% |
How it has done
WFBIX share class · total returns with dividends reinvested
Volatility over the last 12 months: 3.38%. Past returns are a record, not a forecast.
Jun 2026 has been filed since the trailing figures were struck, so it is not in the table above or the curve — every figure here shares one cut-off, which is what makes them comparable with other funds.
This fund changed legal form during the period shown. The history above is continuous — it spans both eras, and the change is not a gap in reporting.
Fees & fund details
iShares U.S. Aggregate Bond Index Fund is a U.S. equity index fund that tracks the Bloomberg U.S. Aggregate Bond Index.
- Asset class
- Equity
- Region
- United States
- Management
- Index (passive)
- Fund type
- Open-end fund
- Features
- Master-feeder
- Expense ratio, by class
- 0.05% – 0.35%· WFBIX 0.05%
- Portfolio turnover
- 93.00% a year · as of 2026 Q2
Turnover is how much of the portfolio was replaced in a year.
Classified from what the fund holds, not from its name · 2026 Q2. The summary is a paraphrase of the prospectus; the objective is verbatim.
What changed this quarter
Positions that entered or left the fund since its previous filing. Positions that were only resized are not listed.
New and exited totals aren’t verifiable for this fund.
Understand how this fund fits with the rest.
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