# MBB (iShares MBS ETF)

iShares · Bond ETFs · Government mortgage-backed · data as of Oct 28, 2026

MBB returned −0.8% over the year to Oct 28, 2026, charges 0.04% a year and holds $35.5bn in net assets on Oct 28, 2026.

Promise check: Delivered. Over the year to Oct 28, 2026, MBB returned −0.8% against −1.1% for SPMB, which tracks the same Bloomberg U.S. MBS Index. Fees aside, MBB finished 0.30 points ahead of SPMB. https://etfiq.com/promise-index/bonds/

MBB tracks an index of mortgage-backed securities and returned −0.8% over the past year.

## Key facts

- MBB, total return, 1 year: −0.8%, as of Oct 28, 2026.
- MBB, expense ratio: 0.04%, as of Jun 18, 2026.
- MBB, holdings: 10813, as of Oct 27, 2026.
- MBB, below its high: −2.9%, as of Oct 28, 2026.
- MBB, 12-month yield, capital gains included, on its starting price: 4.2%, as of Oct 28, 2026.
- MBB, last payment (paid monthly), ex-date Oct 1, 2026: $0.3662, as of Oct 1, 2026.
- MBB, net assets: $35.5bn (the issuer’s own daily fund list, as of Oct 28, 2026).

## MBB over each window to Oct 28, 2026

| Window | Total return | Benchmark (SPMB) | Gap to SPMB |
| --- | --- | --- | --- |
| 1 month | +2.4% | +2.1% | +0.3 pts |
| 3 months | −0.8% | −1.1% | +0.3 pts |
| 6 months | −1.2% | −1.4% | +0.2 pts |
| Year to date | −0.8% | −1.0% | +0.2 pts |
| 1 year | −0.8% | −1.1% | +0.3 pts |
| 3 years | +19.2% | +18.8% | +0.4 pts |
| 5 years | +0.6% | +0.4% | +0.2 pts |
| 10 years | +11.4% | +10.5% | +0.9 pts |
| Since launch | +63.8% | not available | not available |
| Since launch, annualised | +2.5% | – | – |

## MBB key stats

- 52-week high, daily closes to Oct 28, 2026: $96.91 on Feb 27, 2026 (computed by ETFIQ from Tiingo daily prices)
- 52-week low, daily closes to Oct 28, 2026: $89.09 on Oct 5, 2026 (computed by ETFIQ from Tiingo daily prices)
- Close on Oct 28, 2026, within that range: $91.41, 30% of the way from the low to the high (computed by ETFIQ from Tiingo daily prices)
- Beta to its benchmark, 1 year: 1.02, against SPMB (computed by ETFIQ from Tiingo daily prices)
- R-squared, the same days: 0.96 (computed by ETFIQ from Tiingo daily prices)
- Beta and R-squared measured over: 251 daily total returns, Oct 29, 2025 to Oct 28, 2026 (computed by ETFIQ from Tiingo daily prices)
- Holdings: 10813
- Top ten weight: 10.8%

## MBB trading

- IQ Liquidity Score 90, Trades like a giant, 73rd percentile of 200 bonds ETFs.
- Trades like a giant: trades at a typical spread of 0.01%.
- $1,000: at least $0.05, 0.005%, one way, half a one-cent tick.
- $10,000: at least $0.55, 0.005%, one way, half a one-cent tick.
- Full cost to own, 1 year at $10,000: 0.11%, against 0.04% for the fee alone.
- Premium to NAV at the Oct 28 close: +0.10%; 95% of days within ±0.15%.
- Limit: midpoint + 1¢ to buy, midpoint − 1¢ to sell. At the Oct 28 close of $91.41, that’s $91.42 to buy and $91.40 to sell.
- The full trading page: https://etfiq.com/funds/mbb/trading/

## Every published field

| Field | Value | Source |
| --- | --- | --- |
| What it tracks | Bloomberg U.S. MBS Index | ETFIQ |
| Fund type | Bond fund | ETFIQ |
| Category | Bonds · Government mortgage-backed | ETFIQ |
| Expense ratio | 0.04% | 485BPOS XBRL, Jun 18, 2026 |
| Price | $91.41 | ETFIQ |
| First traded | Mar 16, 2007 | ETFIQ |
| Net assets | $35.5bn | the issuer’s own daily fund list, as of Oct 28, 2026 |
| Benchmark | Bloomberg U.S. MBS Index, measured by SPMB, which tracks the same index | ETFIQ, from its filings |
| Benchmark named in | its prospectus, 485BPOS, Jun 18, 2026 | ETFIQ |
| MBB, 1 year to Oct 28, 2026 | −0.8% | ETFIQ |
| SPMB, the same days | −1.1% | ETFIQ |
| Against its benchmark, 1 year | +0.3 pts | ETFIQ |
| Below its high | −2.9% | ETFIQ |
| Holdings | 10813 | ETFIQ |
| Top ten weight | 10.8% | ETFIQ |
| Holdings published for | Oct 27, 2026 | the issuer’s daily file |
| Holdings as of the close of | Oct 27, 2026 | the issuer’s daily file |

## Money in and out, to Oct 23, 2026

| Window | Dates | Net flow |
| --- | --- | --- |
| 1 week | Oct 21, 2026 to Oct 23, 2026 | $0 |
| 1 month | Sep 28, 2026 to Oct 23, 2026 | −$1.9bn |
| 3 months | Jul 28, 2026 to Oct 23, 2026 | −$2.7bn |
| Year to date | Jan 2, 2026 to Oct 23, 2026 | −$1.8bn |
| 1 year | Oct 28, 2025 to Oct 23, 2026 | −$4.8bn |

Computed by ETFIQ from the change in shares outstanding times the previous day’s NAV. Every day and month: <https://etfiq.com/data/flows/funds/mbb.json>. Method: https://etfiq.com/methodology/flows

## Questions

### How has MBB performed?

Over the year to Oct 28, 2026, MBB returned −0.8% with distributions reinvested, against −1.1% for its benchmark, the Bloomberg U.S. MBS Index. Over three years the number is +19.2%.

### What does MBB cost?

The prospectus expense ratio is 0.04% a year.

### How far is MBB below its high?

2.9% below its high of Feb 27, 2026, measured on the reinvested series to Oct 28, 2026.


## Cite this page

ETFIQ, MBB, bond fund, data as of Oct 28, 2026. https://etfiq.com/funds/mbb
Free to use with attribution for data ETFIQ computes; issuer data stays under its owner's terms. The underlying files are at <https://etfiq.com/data/>.

HTML: https://etfiq.com/funds/mbb  ·  JSON: https://etfiq.com/funds/mbb.json