<prompt> Human: Are there procons with using TreasuryDirect instead of short term treasury funds such as VFISX for super-short fixed income exposure?  <response>: Treasury Direct pros: Can buy with as little as 100 each time. Can autopurchase with direct deposit.Cons: One more account to manage, and its a single-purpose account. Cant sell early.Brokerage account:Pros: Can buy ultrashort and short-term mutual funds both index and active; there are valid arguments for active in the bond market at no commission. Which ones depend on brokerage. Can buy and sell short-term treasury and floating rate investment grade corporate bond ETFs at no commission which ones again depend. Can buy and sell treasury billsnotesbonds at no commission, both new issues and secondaries. e.g. buying the last 3 months of a 10-year bond, or buying next Mondays 3-month auction. Multipurpose account that also can hold moneymarket funds and brokered FDIC-insured CDs. Single statement, website, and app, and single year-end tax statement. All kinds of free and low-cost money movement tofrom banks, wires at low cost, etc. Cons: Investing in any particular thing is separate action from putting money into the account itself. Treasuries trade at 1000 minimum including at new issue auction, 10X the minimum at Treasury Direct. Autoinvest only works with mutual funds, not ETFs nor anything else, and is still a separate thing to set up from the automatic get-money-in-account thing. Only these are principal cant change investments: Treasuries bought new and held to maturity, other bonds bought new and held to maturity, money market funds, brokered CDs bought new and held to maturity. Everything else can and will have some principal variation up and down. Maybe worth it, of course, given the overall return, but not stable. That includes your VFISX example. Only the FDIC-ínsured brokered CDs, and the Treasuries, are guaranteed money in that your principal is guaranteed, not just the existence of your holding at whatever its market value is. Its highly unlikely that a MMF will break the buck especially post-2015-regulation, and even more unlikely if the underlying investments in the MMF are US Treasuries only like the all-treasuries MMFs, but it is theoretically possible. If youre not disciplined, the existence of other types of securities you can invest in through the same account, might tempt you into more risk than you wantneed.Overall Id strongly prefer doing a good brokerage account that allows choice in what you can buy, but do be aware of the pros and cons. If you are doing small amounts on monthly intervals and want absolute security, then Treasury Direct or an online high-yield savings bank are better choices. 