VGUS seeks to track an index of investment grade US Treasury bills that have maturities of less than one year. Securities are selected and weighted based on their market value. This fund seeks to maintain a dollar-weighted average maturity consistent with that of the index which is expected to be from one to twelve months. The fund employs a sampling strategy, aiming to have a similar exposure to its index by holding a range of securities similar to the full index in terms or key risks factors and other characteristics. The fund may also invest in debt securities that are not included in the Index, cash and cash equivalents, or money market instruments, such as repurchase agreements and money market funds.