iShares MBS ETF (NASDAQ:MBB) — Agency mortgage backed securities in focus

Sonal Goyal

05 November 2026 12:57 PM AEDT

iShares MBS ETF (NASDAQ:MBB) — Agency mortgage backed securities in focus

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Highlights

Exposure focus: Agency Mortgage backed securities in focus.
Official net Assets were USD 35,894,631,260 as at 4 November 2026.
The listed net annual expense ratio is 0.04%.
Its reference measure is Bloomberg U.S. MBS Index.

iShares MBS ETF (NASDAQ:MBB) holds exposure to US agency mortgage-backed securities. These securities pass through cash flows associated with mortgage pools. Homeowner refinancing and repayment behavior can alter the timing of those cash flows, making mortgage bonds behave differently from otherwise comparable bonds with fixed repayment schedules.

Investment approach and market coverage

iShares MBS ETF (NASDAQ:MBB) uses an index-tracking mandate. The stated benchmark is Bloomberg U.S. MBS Index. The benchmark defines the eligible Investment universe, and its membership and weights shape the portfolio. An index objective does not mean the fund and benchmark will match exactly. Expenses, transactions, cash balances and implementation decisions can create differences. The scope of the mandate matters when comparing this exposure with an existing portfolio, because funds with similar names may cover different securities or market segments.

Holdings and underlying exposure

In the official holdings file dated 3 November 2026, selected leading individual bond positions were Fhlmc 30Yr Umbs Super maturing 1 May 2051 at 1.05%; Umbs 30Yr Tba(Reg A) maturing 12 November 2026 at 0.76%; Gnma2 30Yr Tba maturing 19 November 2026 at 0.70%; Gnma2 30Yr maturing 20 November 2054 at 0.59%; Gnma2 30Yr maturing 20 October 2051 at 0.54%. These figures are security-level portfolio weights; separate securities from the same issuer may appear in other rows. Holdings and weights can change.

Aggregating the reported bond rows by the issuer file’s sector labels gives Agency Fixed Rate at approximately 95.00%, Hybrid Arms at approximately 0.00%. These are calculated sums of rounded security weights, rather than a separate issuer-published allocation table. Cash, Derivatives and other asset classes are excluded from these sector sums. The composition helps explain which economic exposures accompany the stated mandate.

Fees distributions and share pricing

iShares MBS ETF (NASDAQ:MBB) has a listed gross annual expense ratio of 0.04% and net annual expense ratio of 0.04%. At the net rate, USD 10,000 held at a constant value for a full year would imply approximately USD 4.00 in annual fund expenses. This is an illustrative fee calculation, excluding changes in value, brokerage costs and bid-ask spreads. Expenses are reflected within the product rather than quoted as a promised investment outcome.

The stated distribution frequency is monthly. The schedule describes how often distributions are expected, while payment amounts depend on income and other applicable fund circumstances. A distribution is distinct from Capital appreciation and does not establish a fixed future payment. Shareholders also need to consider their own tax treatment, including any treatment of distributions or gains on sale.

iShares reported net asset value of USD 91.97 per share as at 4 November 2026. NAV measures the underlying net asset value allocated to a share; it is not an exchange closing-price quotation. Shares trade on NASDAQ, where the transaction price can differ from NAV and where the bid-ask spread adds to the cost of entering or exiting a position.

Prepayments and extension risk

Mortgage-backed securities have uncertain principal repayment timing because borrowers can refinance or repay early. Faster repayments can require reinvestment at lower available yields. When rates rise, repayments may slow, extending the effective life of the exposure. These prepayment and extension effects make mortgage bonds respond differently from Debt with a fixed principal schedule. Agency exposure does not prevent changes in the Market Value of the fund.

Key Insights

iShares MBS ETF (NASDAQ:MBB) is defined by its benchmark and eligible investment universe. Its holdings explain the actual exposure, while the fee schedule and distribution arrangements explain important ownership mechanics. These features need to be considered together: broad coverage, a particular style or a specified Maturity band each changes the risks a Shareholder takes. The investment objective remains a target, and the value of the shares can decline.

Data checked on 5 November 2026. Each numerical observation uses the specific source date stated above.

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