The Pop-Up Unit (an available option below), slides out from under your daybed to accept a second twin mattress (39"x75") for that unexpected guest. This gives you a sleep surface of about 76"x75" which is the width of a king size bed! This unit is built with safety in mind. Gravity locks prevent inadvertent release, while tension spring tabs lock the activation bar securely in place. Features include galvanized helical spring suspension, and two cross supports for added stability and comfort.