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MBB vs SPMB: Differences, Returns & Fees

MBB's duration was 5.4 years on May 31, 2026 and SPMB's 5.5 on Jun 30, 2026; both charge 0.04%. Net assets: $35.6bn on Oct 9, 2026 for iShares MBS ETF, and $6.8bn on Oct 8, 2026 for State Street SPDR Portfolio Mortgage Backed Bond ETF.

Both cost 0.04% a year; their one-year returns differ by 0.2 points; MBB is 5.2 times larger.

Points (pts) are percentage points.

MBBSPMB
Expense ratio0.04%0.04%
Net assets, as of Oct 8, 2026$35.6bn$6.8bn
Total return, 1 year−1.2%−1.4%
What it tracksBloomberg U.S. MBS IndexBloomberg U.S. MBS Index ?
Holdings in common14%
Below its high4.6%, high on Feb 27, 20264.7%, high on Feb 27, 2026

Holdings in common uses holdings dated May 31, 2026 and Jun 30, 2026.

−1.2%
MBB total return, 1 year
−1.4%
SPMB total return, 1 year
0.04%
MBB expense ratio
0.04%
SPMB expense ratio

What they hold in common

By the books each fund has filed, MBB and SPMB hold 14% of their money in the same securities at the same weight. Above 50%, holding both is close to holding one of them twice. Holdings dated May 31, 2026 and Jun 30, 2026.

half

14% in common

Positions both hold, largest shared weight first
Holding MBB SPMB
Fannie Mae Pool, due Nov 1, 2051 0.44% 0.47%
Fannie Mae Pool, due Oct 1, 2051 0.31% 0.37%
Ginnie Mae II Pool, due Jan 20, 2052 0.31% 0.30%
Freddie Mac Pool, due Apr 1, 2051 0.50% 0.30%
Fannie Mae Pool, due Apr 1, 2051 0.30% 0.26%
Ginnie Mae II Pool, due Aug 20, 2051 0.30% 0.25%
Ginnie Mae II Pool, due Dec 20, 2050 0.28% 0.25%
Ginnie Mae II Pool, due May 20, 2051 0.35% 0.22%
Fannie Mae Pool, due Feb 1, 2052 0.22% 0.45%
Ginnie Mae II Pool, due Dec 20, 2051 0.53% 0.20%
Ginnie Mae II Pool, due Mar 20, 2052 0.36% 0.18%
Ginnie Mae II Pool, due Apr 20, 2052 0.23% 0.18%
Only in MBB
Freddie Mac Pool, due May 1, 2051 1.05%
Ginnie Mae, due Jun 20, 2056 0.95%
Uniform Mortgage-Backed Security, TBA, due Jun 1, 2056 0.83%
Ginnie Mae, due Jun 20, 2056 0.67%
Uniform Mortgage-Backed Security, TBA, due Jun 1, 2056 0.64%
Ginnie Mae II Pool, due Nov 20, 2054 0.55%
Ginnie Mae II Pool, due Oct 20, 2051 0.54%
Fannie Mae Pool, due Dec 1, 2051 0.52%
Only in SPMB
Freddie Mac Pool, due Feb 1, 2056 1.17%
Freddie Mac Pool, due Aug 1, 2055 0.76%
Uniform Mortgage-Backed Security, TBA, due Jul 1, 2056 0.63%
Freddie Mac Pool, due May 1, 2052 0.61%
Freddie Mac Pool, due Nov 1, 2054 0.55%
Fannie Mae Pool, due Aug 1, 2052 0.51%
Uniform Mortgage-Backed Security, TBA, due Jul 1, 2056 0.46%
Uniform Mortgage-Backed Security, TBA, due Jul 1, 2056 0.45%

Check overlap with more funds →

On the same fields

MBB
iShares MBS ETF
SPMB
State Street SPDR Portfolio Mortgage Backed Bond ETF
Where it sits Bond ETF Bond ETF
Issuer iShares State Street
What it is Tracks an index of mortgage-backed securities Tracks an index
Total return, 1 year −1.2% −1.4%
S&P 500 over the same days +17.3% +17.3%
Gap to the S&P 500 −18.5 pts −18.7 pts
Expense ratio 0.04% 0.04%
Holdings 10855 2756
Net assets, MBB as of Oct 9, 2026 and SPMB as of Oct 8, 2026 $35.6bn $6.8bn

MBB and SPMB on the fields both publish, as of Oct 9, 2026. Source: ETFIQ.

MBB in plain words

MBB tracks an index of mortgage-backed securities. Over the year to Oct 9, 2026 it returned −1.2% with distributions reinvested, against −1.4% for its benchmark, the Bloomberg U.S. MBS Index. The prospectus expense ratio is 0.04% a year. It sat 4.6% below its high of Feb 27, 2026 on Oct 9, 2026.

SPMB in plain words

SPMB tracks an index. Over the year to Oct 9, 2026 it returned −1.4% with distributions reinvested, against −1.2% for its benchmark, the Bloomberg U.S. MBS Index ?. It sat 4.7% below its high of Feb 27, 2026 on Oct 9, 2026.

Questions people ask

Which returned more over the last year, MBB or SPMB?
In the year to Oct 9, 2026, with distributions reinvested, MBB returned −1.2% and SPMB −1.4%.
Which is cheaper, MBB or SPMB?
Neither: MBB and SPMB both charge 0.04% a year. Fees come from each fund's prospectus.
Other comparisons
MBB vs SMBSMBB vs VMBSMBB vs PMBSJMTG vs MBBFSEC vs SPMBSPMB vs VMBSJMBS vs SPMBPMBS vs SPMB
MBB on its own →SPMB on its own →Hold both: look the portfolio through →Rankings →Standards and sources →
Where these figures came from
MBB filings on SEC EDGAR ↗MBB prospectus with the expense ratio (SEC) ↗iShares page for MBB ↗SPMB filings on SEC EDGAR ↗SPMB prospectus with the expense ratio (SEC) ↗State Street website ↗

ETFIQ links to the documents behind every figure; a link is not an endorsement. A comparison is not a recommendation.

How this is computed

Overlap adds up the smaller of the two weights for each security both funds hold.

Cite this pageCitation, APA and Markdown

ETFIQ, MBB against SPMB, data as of Oct 9, 2026. https://etfiq.com/compare/any/mbb-vs-spmb

Open data

Free to use with attribution for figures ETFIQ computes; issuer data stays under its owner's terms.