CYS Investments (formerly Cypress Sharpridge Investments) is a real estate investment trust (REIT) that invests in residential mortgage-backed securities (RMBS) primarily collateralized by adjustable-rate mortgage loans and guaranteed by government agencies Fannie Mae, Freddie Mac, and Ginnie Mae. (As a REIT, CYS is exempt from paying federal income tax so long as it distributes dividends back to shareholders.) More than three-quarters of its portfolio is backed by hybrid adjustable-rate mortgages (ARMs) and 15-year fixed-rate single-family mortgages. The REIT's investment activities are usually financed through major commercial and investment banks.