MMK vs XHLF

MMKCState Street Prime Money Market ETF

XHLFABondBloxx Bloomberg Six Month Target Duration US Treasury ETF

In short

MMK A money market fund that trades like a stock. MMK is built to qualify under Rule 2a-7, and it's the prime version, so State Street's cash desk underwrites short-term credit instead of sticking to government paper only.

XHLF Most cash-parking funds pick a maturity bucket. XHLF picks a number: it blends Treasury bills to an average duration of about six months, resets to that target monthly, and charges three basis points to do it.

Stated mandate

MMK The Fund seeks to maximize current income while maintaining capital preservation and liquidity.

XHLF The Fund seeks to track the investment results of an index composed of U.S. Treasury securities.

Why people hold it

• MMK Built to qualify as a money market fund under Rule 2a-7, the same rulebook as traditional money funds, but bought and sold intraday like any ETF.ssga.comstatestreet.com
• Prime mandate, run by State Street's cash management team with a dedicated short-term credit research team behind the paper it buys.ssga.com
• Costs 0.18% a year, a shade under the median for cash-alternative ETFs.
• Measured against the ICE BofA SOFR Overnight Rate Index, so there's a plain overnight-cash yardstick to judge it by.ssga.com

• XHLF Costs 0.03% a year, against a typical short-Treasury peer near 0.14%. In cash-like funds, where returns come from bills everyone owns, fee is the main lever.
• Tracks an index built to hold an average duration of roughly six months, rebalanced monthly, so exposure stays anchored instead of drifting as bills mature.bondbloxxetf.com
• Sits in the gap between 0-3 month bill funds and one-year funds. Its sibling XONE targets a one-year duration at the same 0.03%, so the two can be mixed to dial in duration.
• US Treasury bills only, no credit bets hiding in the portfolio, run in a multi-billion-dollar fund that has stayed close to its index.

Worth knowing

• MMK A 2026 launch that is still small and thinly traded, which can mean wider bid-ask spreads than long-running cash ETFs.
• Prime paper carries bank and corporate credit risk that government-only money funds sidestep, and the fund is not FDIC insured.statestreet.com
• Cheaper cash options exist: SBIL and IQMM charge 0.15% and ICSH 0.08%, though those run government or ultra-short bond mandates.

• XHLF Six months of duration is not zero. Prices move a touch more when yields shift than in 0-3 month bill funds such as BIL or CLIP.
• Income rides whatever Treasury bills happen to pay, and distributions arrive on an irregular rhythm rather than a fixed amount or schedule.
• Volume is moderate next to the largest bill ETFs, so spreads can be a bit wider, which matters more on big tickets than small ones.

Full MMK profile⁠

Full XHLF profile⁠