DMBS vs MBB

DMBSCDoubleLine Mortgage ETF

MBBAiShares MBS ETF

In short

DMBS DoubleLine's mortgage desk in an ETF wrapper: an actively managed bond fund built to exceed the Bloomberg U.S. Mortgage-Backed Securities Index over a full market cycle, in a corner of the market almost everyone else simply indexes.

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

DMBS The Fund seeks total return through capital appreciation and current income, exceeding the Bloomberg U.S. Mortgage-Backed Securities Index over a full market cycle.

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

Why people hold it

• DMBS Active by design. Managers pick the mortgage bonds instead of copying the index, with a stated aim of exceeding the Bloomberg U.S. Mortgage-Backed Securities Index over a full market cycle.
• Pays monthly, matching the rhythm of the mortgage cash flows underneath it.
• Trades with decent everyday liquidity for an active bond ETF, and sits in the upper half of its mortgage-bond peer group on our review.
• A US agency mortgage mandate run inside a standard 1940 Act fund. No exotic wrapper, no K-1 surprises.

• 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

• DMBS At 0.39% a year it runs above the typical mortgage-bond ETF, and roughly ten times index trackers like VMBS (0.03%) and MBB (0.04%). Active management has to earn that gap.
• Launched in 2023, so its track record is short relative to the full market cycle the fund itself uses as the yardstick.
• Results ride on the manager's security selection rather than the benchmark, which means the gap versus the index can cut either way.

• 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 DMBS profile⁠

Full MBB profile⁠