有risk，但風險很小。SPAXX有71.68%在repo裏麵，除非repo項目倒閉政府破產，不然不可能不兌現。

https://fundresearch.fidelity.com/mutual-funds/summary/31617H102

Composition by

 Instrument 5 

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AS OF 12/31/2022

U.S. Treasury Bills

0.93%

U.S. Treasury Coupons

6.77%

U.S. Treasury Strips

0.00%

U.S. Treasury Inflation-Protected Securities

0.21%

Agency Fixed-Rate Securities

7.06%

Agency Floating-Rate Securities

13.26%

U.S. Government Repurchase Agreements

71.68%

Other Money Market Investments

0.00%

Net Other Assets

0.09%

Additional Information

Risk

You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Fidelity Investments and its affiliates, the fund's sponsor, have no legal obligation to provide financial support to the fund, and you should not expect that the sponsor will provide financial support to the fund at any time. The fund will not impose a fee upon the sale of your shares, nor temporarily suspend your ability to sell shares if the fund's weekly liquid assets fall below 30% of its total assets because of market conditions or other factors. Interest rate increases can cause the price of a money market security to decrease. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a money market security to decrease.