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 13.1% of net assets.
US Aggregate Bond base · ETF wrapper · 4.42% 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. Seemethodologyfor formulas, thetracking-qualitypartial-coverage rationale, and the dimensions we deliberatelydon't score(methodology v0.5.1).
Use MBB in our tools
Tool · Look-through
See what MBB actually holds, in a portfolio
Add your other funds and weights; every underlying position is summed across the basket.
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 | 6.77% |
| 2 | Freddie Mac | 1.05% |
| 3 | Government National Mortgage Association | 0.95% |
| 4 | UMBS, TBA | 0.83% |
| 5 | Government National Mortgage Association | 0.67% |
| 6 | UMBS, TBA | 0.64% |
| 7 | Government National Mortgage Association | 0.55% |
| 8 | Government National Mortgage Association | 0.54% |
| 9 | Government National Mortgage Association | 0.53% |
| 10 | Fannie Mae | 0.52% |
Compare MBB with another fund
Or skim the closest-overlap funds below.
Similar ETFs by holdings overlap
Open MBB at a brokerage
Affiliate links — opening an account through these earns PlainIndex a one-time referral. Scoring is computed before any affiliate consideration; see our methodologyand funding disclosure.