VMBS offers good exposure to mortgage pass-through securities, efficiently. It has exposure to the three major agencies: Fannie Mae, Freddie Mac and Ginnie Mae. Instead of holding actual MBS pass-throughs, VMBS uses MBS TBAs as liquid alternatives to the MBS. As a Vanguard product, VMBS is a bit less transparent as it does not disclose its holdings daily. In all, VMBS offers good mortgage-backed securities coverage in a stable wrapper.