MBB holdings

Computed by this site from the fund's SEC Form N-PORT filing; what the measure does not tell you · every fund in one table · hold it with other funds? X-ray the mix. Pricing: 6.46% at a quoted market price (level 1), one issuer country.

The largest line in MBB's filing is not a stock but BlackRock Cash Funds: Treasury, SL Agency Shares, a short-term position at 6.77% of net assets. Ten companies are 12.45% of the fund; the other 11,136 share the rest. Among the 15 mortgage-backed funds measured here, MBB behaves like 187.7 holdings against a median of 157.5 — close to the median. Across 27 quarterly filings MBB has become less concentrated: it behaved like 72.8 at 2019-11-30 and 187.7 at 2026-05-31. Between the 2026-02-28 and 2026-05-31 filings 100 positions were added and 82 dropped; 9.1% of the weight moved.

Each sentence is read from the fund's own SEC filing; the class median is computed across the comparable mortgage-backed funds on this site. Nothing here is a view on the fund.

Between 2019-11-30 and 2026-05-31, MBB went from behaving like 72.8 equally weighted positions to 187.7 — 158% more, while its top ten went from 19.28% to 12.45% of net assets. Read across the funds on the concentration-over-time table.

One row per filed reporting period, newest first, read from EDGAR. Quarterly because that is the public filing cadence. Rows marked * are published but held out of the comparison above; the methodology page says when and why.

The 15 largest of 11,146 positions in MBB's Form N-PORT, weight as a share of net assets, securities-lending collateral excluded. Every position, every quarter: listed with the point-in-time files, available on request.

Monthly total returns from Item B.5 of MBB's own filings, 81 months on record. Not computed here and not from a price feed.

Cross-checked against a series computed separately from prices: median difference 0.07 percentage points over 81 months, which is roughly the distributions. Every month with the filing it came from: MBB.json · all funds.

10,674 positions became 10,692: 100 added (7.6% of the fund at the later date), 82 dropped (5.3% at the earlier date). Half the sum of all weight changes, a turnover proxy: 9.1%. Positions are matched on identifiers, so a security whose identifier changed shows as one drop and one add. Every filing of MBB compared this way, as a feed: changes.xml · all funds: filings received.

New: Government National Mortgage Association (0.90%), UMBS, TBA (0.79%), Government National Mortgage Association (0.64%), UMBS, TBA (0.61%), Government National Mortgage Association (0.44%), UMBS, TBA (0.32%). Gone: Government National Mortgage Association (0.96%), UMBS, TBA (0.55%), Government National Mortgage Association (0.51%), UMBS, TBA (0.48%), Government National Mortgage Association (0.44%), UMBS, TBA (0.34%).

93.54% mortgage-backed, 6.46% short-term investment as filed; 6.5% carried at a quoted market price (fair-value level 1). Categories and levels are the filer's; what a low level-1 share does and does not mean is in the measure's page.

Every measured mortgage-backed fund lined up by how many holdings it behaves like; these sit either side of MBB (187.7). Same filings, same arithmetic. Position in this list says nothing about which fund is better.