Data as of Sep 12, 2026. Both funds on the fields they both publish, from the same sources.
IUSB vs MBB: how they differ
IUSB and MBB hold 11% of their weight in the same names.
iShares Core Universal USD Bond ETF and iShares MBS ETF.
What they hold in common
By the books each fund has filed, IUSB and MBB hold 11% of their money in the same securities at the same weight.
| Holding | IUSB | MBB |
|---|---|---|
| Government National Mortgage Association | 0.21% | 0.16% |
| Government National Mortgage Association | 0.12% | 0.31% |
| Federal Home Loan Mortgage Corp. | 0.11% | 0.12% |
| Federal National Mortgage Association | 0.10% | 0.33% |
| Government National Mortgage Association | 0.10% | 0.42% |
| Federal Home Loan Mortgage Corp. | 0.10% | 0.18% |
| Federal National Mortgage Association | 0.10% | 0.17% |
| Government National Mortgage Association | 0.10% | 0.56% |
| Government National Mortgage Association | 0.09% | 0.54% |
| Federal National Mortgage Association | 0.09% | 0.14% |
| Government National Mortgage Association | 0.09% | 0.13% |
| Federal National Mortgage Association | 0.08% | 0.45% |
| Only in IUSB | Only in MBB |
|---|---|
| United States of America 0.38% | Government National Mortgage Association 0.97% |
| United States of America 0.37% | UMBS, TBA 0.85% |
| United States of America 0.37% | Government National Mortgage Association 0.69% |
| United States of America 0.37% | UMBS, TBA 0.66% |
| United States of America 0.36% | Government National Mortgage Association 0.47% |
| United States of America 0.36% | Government National Mortgage Association 0.37% |
| United States of America 0.36% | UMBS, TBA 0.34% |
| United States of America 0.35% | Fannie Mae 0.33% |
Weight overlap is an ETFIQ calculation: for every security both funds hold, the smaller of the two weights, summed. Above 50%, holding both is close to holding one of them twice. Holdings dated Apr 30, 2026 and May 31, 2026.
| IUSB iShares Core Universal USD Bond ETF | MBB iShares MBS ETF | |
|---|---|---|
| Where it sits | Core index fund | Core index fund |
| Issuer | iShares | iShares |
| What it is | Core Universal USD Bond | Mbs |
| Total return, 1 year | −0.3% | −0.1% |
| S&P 500 over the same days | +17.5% | +17.5% |
| Gap to the S&P 500 | −17.8 pts | −17.6 pts |
| Expense ratio | 0.06% | 0.04% |
| Holdings | 17819 | 11144 |
IUSB in plain words
IUSB is a bond fund tracking the Core Universal USD Bond. Over the year to Sep 11, 2026 it returned −0.3% with distributions reinvested, against +17.5% for the S&P 500 and +23.0% for the Nasdaq-100. The prospectus expense ratio is 0.06% a year.
MBB in plain words
MBB is a bond fund tracking the Mbs. Over the year to Sep 11, 2026 it returned −0.1% with distributions reinvested, against +17.5% for the S&P 500 and +23.0% for the Nasdaq-100. The prospectus expense ratio is 0.04% a year. It sat 3.3% below its high of Feb 27, 2026 on Sep 11, 2026.
Questions people ask
- Which returned more over the last year, IUSB or MBB?
- In the year to Sep 12, 2026, with distributions reinvested, IUSB returned −0.3% and MBB returned −0.1%, so MBB returned more. One year is one year; the longer windows are in the table.
- Which is cheaper, IUSB or MBB?
- IUSB charges 0.06% a year and MBB charges 0.04%, so MBB is cheaper. Fees come from each fund's prospectus.
Other comparisons
Where to next
Where these figures came from
ETFIQ links to the documents behind every figure. It is not affiliated with any issuer, and a link is not an endorsement.
Cite this page. ETFIQ, IUSB against MBB, data as of Sep 12, 2026. https://etfiq.com/compare/any/IUSB-MBB Free to use with attribution; the underlying files are at Open data.
A comparison is not a recommendation. Standards and sources