LMBS vs MBB

LMBSCFirst Trust Low Duration Opportunities ETF

MBBAiShares MBS ETF

In short

LMBS Most mortgage-bond ETFs just clone an index. LMBS hires a manager to hunt current income across roughly 1,100 mortgage positions, keeps the duration short, and pays out monthly. Active where the category is mostly autopilot.

MBB Launched in 2007, MBB is the plain-vanilla way to own U.S. agency mortgage bonds: one of the biggest and busiest funds in a small niche, tracking the Bloomberg U.S. MBS Index for four basis points.

Stated mandate

LMBS The fund is actively managed and primarily seeks current income, with capital appreciation as a secondary objective.

MBB The fund seeks to track an index composed of U.S. agency mortgage-backed securities.

Why people hold it

• LMBS Actively managed, not index-bound: the team pursues current income first, with capital appreciation as a secondary goal, so the mix reflects live judgment on mortgage paper.
• Income arrives monthly rather than quarterly, spread across roughly 1,100 bond positions instead of a handful of big-ticket holdings.
• Multi-billion-dollar fund that trades actively, so getting in and out is generally straightforward rather than a hunt for a counterparty.
• Running since 2014, giving the active approach a decade-plus history through a full swing in interest rates.

• MBB Four basis points to rent the entire agency mortgage market, against a category median near 0.35%. In low-coupon bond land, that gap compounds quietly.
• Scale is the real feature: one of the largest and most actively traded funds in the mortgage-bond category, which generally shows up as tighter spreads.
• Pays monthly, and the mandate stays narrow: an index of U.S. agency mortgage-backed securities, nothing exotic bolted on.
• Among the stronger builds in a thin peer group of mortgage-bond ETFs, on the combination of cost, trading friction and issuer staying power.

Worth knowing

• LMBS Active talent is not cheap: 0.66% a year against a 0.35% median for mortgage-bond ETFs, while index rivals VMBS (0.03%) and MBB (0.04%) charge a rounding error.
• No benchmark to lean on. What you own shifts with the manager's calls on which mortgage bonds to hold, which is the whole point and the whole risk.
• This is a focused mortgage-bond sleeve, not a broad core bond fund, so the exposure stays concentrated in one corner of the credit market.

• MBB This is one slice of the bond market. Agency mortgage paper only, with no Treasuries or corporates alongside it.
• Mortgage bonds cut both ways with rates: borrowers refinance when yields fall and sit tight when they rise, so the portfolio's duration shifts underneath you.
• On price it's a photo finish: SPMB tracks the same index at the same 0.04%, and VMBS runs a basis point cheaper.

Full LMBS profile⁠

Full MBB profile⁠