The Zinus Core Comfort 6 in Twin is a low-profile innerspring mattress designed for compact sleep setups. Its slim 6 in profile makes it a practical pick for bunk beds, trundles, daybeds, and tight spaces where a thicker mattress wouldn't fit. Inside, a sturdy Bonnell-coil innerspring base works with a foam layer and a tight-top design to create a firm, smooth, even sleeping surface. It arrives compressed in a compact box for easy handling. After unboxing, please allow 24-72 hours for the mattress to fully expand to its full shape.