iShares MBS ETF
iShares · Tracks Bloomberg US MBS Index · Inception Mar 13, 2007
Composite score
Based on a 0.040% expense ratio.
Based on $39.63B in net assets.
Top-10 holdings represent 11.7% of net assets.
US Aggregate Bond base · ETF wrapper · 4.30% TTM yield.
The composite is a weighted average of the four core sub-scores above (cost, tax efficiency, liquidity, concentration). Missing sub-scores fall back to the per-category median when the category has at least 50% data coverage, so funds without (e.g.) parsed N-PORT holdings aren't accidentally boosted by renormalization. Tracking quality is shown where computable but isn't currently part of the composite weighting. See methodology for formulas, the tracking-quality partial-coverage rationale, and the dimensions we deliberately don't score (methodology v0.5.1).
Use MBB in our tools
Tool · Cost
Compare MBB's fee against another fund
Compounds the 0.040% expense ratio against a peer over decades.
Tool · Overlap
Compare MBB's holdings with peers
Pairwise holdings heatmap, pre-loaded with similar US Aggregate Bond funds.
Tool · TLH
Find a tax-loss harvesting partner for MBB
Ranks every catalog fund by holdings overlap, flags wash-sale risk.
Tool · Placement
Where should this fund live across your accounts?
Asset-location optimizer — places each fund in taxable / tax-deferred / Roth.
Top holdings
| # | Holding | Weight |
|---|---|---|
| 1 | BLACKROCK CASH FUNDS | 5.90% |
| 2 | Freddie Mac | 1.07% |
| 3 | Government National Mortgage Association | 1.00% |
| 4 | UMBS, TBA | 0.57% |
| 5 | Government National Mortgage Association | 0.56% |
| 6 | Government National Mortgage Association | 0.55% |
| 7 | Fannie Mae | 0.53% |
| 8 | Government National Mortgage Association | 0.53% |
| 9 | Freddie Mac | 0.51% |
| 10 | UMBS, TBA | 0.50% |
Compare MBB with another fund
Or skim the closest-overlap funds below.
Similar ETFs by holdings overlap
- VMBS Vanguard Mortgage-Backed Securities Index Fund ETF Shares 18.4% overlap
- AGG iShares Core U.S. Aggregate Bond ETF 17.4% overlap
- SPMB State Street SPDR Portfolio Mortgage Backed Bond ETF 15.0% overlap
- EAGG iShares ESG U.S. Aggregate Bond ETF 13.5% overlap
- IUSB iShares Core Universal USD Bond ETF 10.3% overlap
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