MBBvsMFSMETF Comparison
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iShares MBS ETF (MBB) belongs to the MBS & ABS segment. MFS Active Intermediate Muni Bond ETF (MFSM) is part of the Municipal Bonds segment. MBB's top 3 sector exposures are Industrials, Non-Corporate and Finance. In contrast, MFSM's top sector exposures are Municipal. MBB is less expensive with a Total Expense Ratio (TER) of 0.04%, versus 0.34% for MFSM. MBB is down -1.34% year-to-date (YTD) with +$1.52B in YTD flows. MFSM performs better with -1.14% YTD performance, and +$53M in YTD flows. Run a side-by-side ETF comparison of MBB and MFSM below, and assess how they stack up in performance, liquidity, risk, exposure, holdings, and more, helping you select the best ETF for your investments.
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MBB vs MFSM performance and flow charts
Performance
Cumulative Flows
Historic performance and flows
Data as of 09/11/2026
| 1M | 3M | YTD | 1Y | 3Y | 5Y | ||
|---|---|---|---|---|---|---|---|
| Perf. | MBB MFSM | -1.48%-2.52% | -2.24%-2.93% | -1.34%-1.14% | -0.12%+0.85% | +13.76%n/a | -0.62%n/a |
| Flows | MBB MFSM | +$655M+$2M | +$892M+$7M | +$1.52B+$53M | -$888M+$57M | +$12.43B- | +$17.94B- |
Volatility and drawdown
| 3M | 1Y | 3Y | 5Y | ||
|---|---|---|---|---|---|
| Volatility | MBB MFSM | +4.76%+2.94% | +4.22%+2.33% | +5.85%n/a | +6.60%n/a |
| Max drawdown | MBB MFSM | -2.79%-3.53% | -3.37%-3.53% | -5.44%n/a | -17.29%n/a |
| Max drawdown duration | MBB MFSM | 74d66d | 194d66d | 75dn/a | 1492dn/a |
Trading data
MBB | MFSM | |
Last sale 9/11/2026 at 1:30 PM | $91.38 | $24.16 |
| Previous close 09/10/2026 | $91.48 | $24.14 |
| Consolidated volume 09/10/2026 | ||
| Average volume 30 days | ||
| Average discount or premium 30 days | ||
| Average Bid/Ask spread 30 days |
Replication quality
Data as of August 31, 2026
1-year trailing difference
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MFSM
is actively managed and doesn’t replicate an indexMBB | MFSM | |
|---|---|---|
| Tracking error | ||
| Tracking difference | ||
| 1 year cumulative return difference | ||
| Best | ||
| Worst | ||
| Daily return difference | ||
| Average | ||
| Worst | ||
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Main metrics
Last update 9/11/2026 at 1:30 PM
Live
Closed
MBB | MFSM | |
|---|---|---|
| Last price | $91.38 | $24.16 |
| 1D performance | -0.11% | +0.10% |
| AuM | $38.92 B | $101.93 M |
| E/R | 0.04% | 0.34% |
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Exposure
Countries
MBB
USA
29.07%
Other
70.93%
MFSM
USA
27.33%
Other
72.67%
Sectors
MBB
Industrials
20.93%
Non-Corporate
7.91%
Other
71.16%
MFSM
Municipal
27.33%
Other
72.67%
Diversification
MBB
Total weight of top 15 holdings out of 15
16.01%
MFSM
Total weight of top 15 holdings out of 15
10.5%
Top 15 holdings
Data as of July 31, 2026
MBB
BlackRock Cash Funds - Institutional
7.91%
FR SD8146, 2% 1may2051, USD (ABS)
1.00%
US21H0526861
0.98%
US01F0506844
0.66%
US21H0506806
0.58%
US01F0526800
0.56%
G2 MB0025, 5% 20nov2054, USD (ABS)
0.53%
G2 MA7648, 2% 20oct2051, USD (ABS)
0.52%
US36179WTX64
0.51%
FN MA4492, 2% 1dec2051, USD (ABS)
0.50%
FR SD8140, 2% 1apr2051, USD (ABS)
0.48%
US21H0426872
0.46%
US21H0606895
0.45%
US36179WJR07
0.44%
FN MA4465, 2% 1nov2051, USD (ABS)
0.43%
MFSM
US49126RAC07
1.00%
US60416UV512
0.94%
Oklahoma Public Property Authority, 5% 1jun2034, USD (2026)
0.83%
Missouri Health and Educational Facilities Authority, 5% 1apr2036, USD (2026A)
0.83%
US708692CB22
0.75%
California Community Choice Financing Authority, 5% 1dec2055, USD (2025C)
0.72%
US763056DQ86
0.72%
US702538FE43
0.71%
US95235TAW36
0.69%
Paulding Hospital Authority, 5% 1apr2036, USD
0.55%
St. Cloud, 5% 1may2036, USD (2026)
0.55%
US164555EB63
0.55%
US49121DAB82
0.55%
US75989FAM59
0.55%
St. Tammany Parish Hospital Service District №1, 5% 1jul2056, USD (2026A)
0.55%
Frequently asked questions about MBB and MFSM
How have the MBB and MFSM ETFs performed in 2026?
As of September 11, 2026, MBB is down -1.34% year-to-date (YTD), while MFSM has lost -1.14%. That puts MFSM better performer ahead so far this year.
Which ETF is attracting more investor money: MBB or MFSM?
Year-to-date, the MBB ETF saw +$1.52B in flows, compared to +$53M for MFSM.
Which ETF is more volatile: MBB or MFSM?
Over the past year, MBB had a volatility of 4.22%, while MFSM experienced 2.33%.
Which ETF is bigger: MBB or MFSM?
As of September 11, 2026, MBB holds $38.92 B in assets under management (AUM), while MFSM manages $101.93 M.
What sectors do the MBB and MFSM ETFs invest in?
MBB leans toward sectors like Industrials and Non-Corporate. Meanwhile, MFSM focuses on Municipal.
What are the top holdings of the MBB ETF and MFSM ETF?
MBB top holdings include BlackRock Cash Funds - Institutional, FR SD8146, 2% 1may2051, USD (ABS) and US21H0526861. MFSM holds in its top three: US49126RAC07, US60416UV512 and Oklahoma Public Property Authority, 5% 1jun2034, USD (2026).
Which ETF is more diversified: MBB or MFSM?
MBB holds 9388 securities with 16.01% of its assets in the top 15. MFSM has 409 securities and a top 15 weight of 10.5%.
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Latest news about MBB & MFSM
What's the Fund | MFS Active Intermediate Muni Bond ETF (MFSM)
July 25, 2025
MFSM
NYSE x ETF Central ETF Education Series
March 5, 2024
MBB
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