{
  "page": "compare",
  "query": {
    "a": "MBB",
    "b": "IUSB"
  },
  "retrieved_at": "2026-07-07T15:43:35+00:00",
  "disclaimer": "Informational only — not investment advice. FundWatcher presents publicly available data and makes no recommendation to buy or sell any security. Verify all figures against the source filing before relying on them.",
  "attribution": "Data sourced from U.S. SEC EDGAR filings (Forms N-PORT, N-CEN, and prospectus Risk/Return summaries). FundWatcher is not affiliated with the SEC.",
  "terms": {
    "notice": "Use of this data is subject to the FundWatcher Terms of Service. Information may be used only for personal, non-commercial research and may not be redistributed.",
    "url": "https://fundwatcher.app/terms/"
  },
  "fund_a": {
    "name": "iShares MBS ETF",
    "ticker": "MBB",
    "slug": "MBB",
    "series_id": "S000013702",
    "html_url": "https://fundwatcher.app/funds/MBB/"
  },
  "fund_b": {
    "name": "iShares Core Universal USD Bond ETF",
    "ticker": "IUSB",
    "slug": "IUSB",
    "series_id": "S000045644",
    "html_url": "https://fundwatcher.app/funds/IUSB/"
  },
  "overlap": {
    "coverage_a_by_b": "0.1145365836009398314913723428",
    "coverage_b_by_a": "0.1145365836009398314913723419",
    "shared_count": 1191,
    "as_of": {
      "a": "2026-02-28",
      "b": "2026-01-31"
    },
    "a_top": [
      {
        "name": "BlackRock Cash Funds: Treasury, SL Agency Shares",
        "value": "2349848882.32",
        "weight": "0.05655290",
        "shared": true
      },
      {
        "name": "FR SD8146",
        "value": "427589929.06",
        "weight": "0.01029064",
        "shared": true
      },
      {
        "name": "GNII II 5.5% 03/01/2056 #TBA",
        "value": "399517163.25",
        "weight": "0.00961502",
        "shared": false
      },
      {
        "name": "FNCL 5 3/24",
        "value": "227789172.20",
        "weight": "0.00548211",
        "shared": false
      },
      {
        "name": "G2 MA7648",
        "value": "221285634.59",
        "weight": "0.00532560",
        "shared": true
      },
      {
        "name": "G2 MA7766",
        "value": "217494998.47",
        "weight": "0.00523437",
        "shared": true
      },
      {
        "name": "FN MA4492",
        "value": "212474536.60",
        "weight": "0.00511354",
        "shared": true
      },
      {
        "name": "G2SF 5 3/25",
        "value": "209896727.56",
        "weight": "0.00505150",
        "shared": false
      },
      {
        "name": "FR SD8140",
        "value": "204523050.63",
        "weight": "0.00492218",
        "shared": true
      },
      {
        "name": "FNCL 5.5 3/25",
        "value": "197749445.88",
        "weight": "0.00475916",
        "shared": false
      },
      {
        "name": "G2 MA7472",
        "value": "185938026.36",
        "weight": "0.00447490",
        "shared": true
      },
      {
        "name": "Government National Mortgage Association, TBA",
        "value": "181046291.07",
        "weight": "0.00435717",
        "shared": true
      },
      {
        "name": "FN MA4465",
        "value": "180370505.38",
        "weight": "0.00434091",
        "shared": true
      },
      {
        "name": "Uniform Mortgage-Backed Securities",
        "value": "178332612.01",
        "weight": "0.00429186",
        "shared": true
      },
      {
        "name": "G2 MB0025",
        "value": "168453696.80",
        "weight": "0.00405411",
        "shared": true
      },
      {
        "name": "G2 MA7935",
        "value": "148438446.26",
        "weight": "0.00357241",
        "shared": false
      },
      {
        "name": "G2 MA7367",
        "value": "144659079.64",
        "weight": "0.00348145",
        "shared": true
      },
      {
        "name": "Uniform Mortgage-Backed Security, TBA",
        "value": "140022705.46",
        "weight": "0.00336987",
        "shared": false
      },
      {
        "name": "FR SD8199",
        "value": "139528303.51",
        "weight": "0.00335797",
        "shared": true
      },
      {
        "name": "FN MA4281",
        "value": "133205700.36",
        "weight": "0.00320581",
        "shared": true
      },
      {
        "name": "Fannie Mae Pool",
        "value": "133096404.12",
        "weight": "0.00320318",
        "shared": false
      },
      {
        "name": "G2 MA9171",
        "value": "130718959.53",
        "weight": "0.00314596",
        "shared": true
      },
      {
        "name": "FN MA4437",
        "value": "127597398.48",
        "weight": "0.00307084",
        "shared": true
      },
      {
        "name": "G2 MA7826",
        "value": "125730376.64",
        "weight": "0.00302590",
        "shared": true
      },
      {
        "name": "G2 MA7534",
        "value": "123557203.52",
        "weight": "0.00297360",
        "shared": true
      },
      {
        "name": "FN MA4305",
        "value": "120559723.67",
        "weight": "0.00290146",
        "shared": true
      },
      {
        "name": "Fannie Mae Pool",
        "value": "115619322.46",
        "weight": "0.00278257",
        "shared": false
      },
      {
        "name": "G2 MA7936",
        "value": "115515880.49",
        "weight": "0.00278008",
        "shared": true
      },
      {
        "name": "G2 MA7051",
        "value": "114056581.14",
        "weight": "0.00274496",
        "shared": true
      },
      {
        "name": "G2 MA7767",
        "value": "112386442.84",
        "weight": "0.00270476",
        "shared": true
      },
      {
        "name": "G2 MA9965",
        "value": "109076526.13",
        "weight": "0.00262510",
        "shared": true
      },
      {
        "name": "FR SD8324",
        "value": "102913588.13",
        "weight": "0.00247678",
        "shared": true
      },
      {
        "name": "FNCL 6 3/24",
        "value": "101312358.87",
        "weight": "0.00243825",
        "shared": false
      },
      {
        "name": "G2 MB0624",
        "value": "100708131.64",
        "weight": "0.00242370",
        "shared": true
      },
      {
        "name": "FR SD8182",
        "value": "96947222.98",
        "weight": "0.00233319",
        "shared": true
      },
      {
        "name": "FANNIE MAE POOL FN 05/52 FIXED VAR",
        "value": "93078582.60",
        "weight": "0.00224009",
        "shared": false
      },
      {
        "name": "G2 MA9781",
        "value": "93019370.83",
        "weight": "0.00223866",
        "shared": true
      },
      {
        "name": "G2 MA7987",
        "value": "92760491.48",
        "weight": "0.00223243",
        "shared": true
      },
      {
        "name": "G2 MA7589",
        "value": "91465086.29",
        "weight": "0.00220125",
        "shared": true
      },
      {
        "name": "FR SD8134",
        "value": "90692946.45",
        "weight": "0.00218267",
        "shared": false
      },
      {
        "name": "FR SD8362",
        "value": "90321930.34",
        "weight": "0.00217374",
        "shared": true
      },
      {
        "name": "Uniform Mortgage-Backed Securities",
        "value": "87655418.50",
        "weight": "0.00210957",
        "shared": true
      },
      {
        "name": "Uniform Mortgage-Backed Securities",
        "value": "87111954.59",
        "weight": "0.00209649",
        "shared": true
      },
      {
        "name": "FR RA5205",
        "value": "87091149.17",
        "weight": "0.00209599",
        "shared": false
      },
      {
        "name": "FNCL UMBS 3.0 CA9308 02-01-51",
        "value": "85646847.71",
        "weight": "0.00206123",
        "shared": false
      },
      {
        "name": "G2 MA9852",
        "value": "84798764.06",
        "weight": "0.00204082",
        "shared": true
      },
      {
        "name": "Uniform Mortgage-Backed Securities",
        "value": "82184209.52",
        "weight": "0.00197790",
        "shared": true
      },
      {
        "name": "G2 MB0091",
        "value": "80607537.41",
        "weight": "0.00193995",
        "shared": true
      },
      {
        "name": "Freddie Mac Pool",
        "value": "79799967.76",
        "weight": "0.00192051",
        "shared": false
      },
      {
        "name": "FR SD8234",
        "value": "77789632.23",
        "weight": "0.00187213",
        "shared": false
      }
    ],
    "b_top": [
      {
        "name": "Blackrock Liquidity TempCash Inst",
        "value": "822411763.60",
        "weight": "0.02300976",
        "shared": false
      },
      {
        "name": "BlackRock Cash Funds: Treasury, SL Agency Shares",
        "value": "277711668.98",
        "weight": "0.00776993",
        "shared": true
      },
      {
        "name": "US TREASURY N/B",
        "value": "136932677.34",
        "weight": "0.00383116",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "135287802.34",
        "weight": "0.00378514",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "134999640.00",
        "weight": "0.00377707",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "134941239.84",
        "weight": "0.00377544",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "132644526.56",
        "weight": "0.00371118",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "132543210.94",
        "weight": "0.00370835",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "126798137.50",
        "weight": "0.00354761",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "124916029.38",
        "weight": "0.00349495",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "122668955.86",
        "weight": "0.00343208",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "120323747.50",
        "weight": "0.00336647",
        "shared": false
      },
      {
        "name": "FN MA4018",
        "value": "119181573.13",
        "weight": "0.00333451",
        "shared": true
      },
      {
        "name": "US TREASURY N/B",
        "value": "117069650.00",
        "weight": "0.00327542",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "114729254.06",
        "weight": "0.00320994",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "114274884.38",
        "weight": "0.00319723",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "109084013.44",
        "weight": "0.00305200",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "105997480.00",
        "weight": "0.00296564",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "104812217.50",
        "weight": "0.00293248",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "98514657.81",
        "weight": "0.00275628",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "98508934.84",
        "weight": "0.00275612",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "97120147.03",
        "weight": "0.00271727",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "95371225.12",
        "weight": "0.00266833",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "94887736.52",
        "weight": "0.00265481",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "94365195.31",
        "weight": "0.00264019",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "93653698.83",
        "weight": "0.00262028",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "93422575.00",
        "weight": "0.00261381",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "92575296.25",
        "weight": "0.00259011",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "92514708.13",
        "weight": "0.00258841",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "91043578.13",
        "weight": "0.00254725",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "91036098.75",
        "weight": "0.00254704",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "88399215.23",
        "weight": "0.00247327",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "87625179.14",
        "weight": "0.00245161",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "86772658.59",
        "weight": "0.00242776",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "86581129.69",
        "weight": "0.00242240",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "86445844.02",
        "weight": "0.00241862",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "85938438.83",
        "weight": "0.00240442",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "85578173.83",
        "weight": "0.00239434",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "85426879.38",
        "weight": "0.00239011",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "83756756.68",
        "weight": "0.00234338",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "83375586.67",
        "weight": "0.00233272",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "82005271.25",
        "weight": "0.00229438",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "80781146.72",
        "weight": "0.00226013",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "80364363.67",
        "weight": "0.00224847",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "80101991.99",
        "weight": "0.00224113",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "79555633.01",
        "weight": "0.00222584",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "79034308.28",
        "weight": "0.00221125",
        "shared": false
      },
      {
        "name": "G2 MA7192",
        "value": "78063240.24",
        "weight": "0.00218408",
        "shared": true
      },
      {
        "name": "US TREASURY N/B",
        "value": "76639482.81",
        "weight": "0.00214425",
        "shared": false
      },
      {
        "name": "US TREASURY N/B",
        "value": "76007421.88",
        "weight": "0.00212657",
        "shared": false
      }
    ]
  },
  "error": null,
  "sources": [
    {
      "label": "N-PORT (fund A)",
      "accession_no": "0001410368-26-039527",
      "as_of": "2026-02-28",
      "edgar_url": "https://www.sec.gov/Archives/edgar/data/1100663/000141036826039527/0001410368-26-039527-index.htm"
    },
    {
      "label": "N-PORT (fund B)",
      "accession_no": "0002071691-26-007327",
      "as_of": "2026-01-31",
      "edgar_url": "https://www.sec.gov/Archives/edgar/data/1100663/000207169126007327/0002071691-26-007327-index.htm"
    }
  ]
}