The 4 Inch Low Profile BiFold Box Spring by Zinus is an innovative folding mattress foundation designed for mobility and functionality. Traditional box springs are hard to maneuver through your home, especially upstairs and through doorways, but the BiFold Box Spring is easy to use in tight places. Tougher than it Looks – Offers the look and functionality of a traditional box spring but made from heavy gauge steel for longer-lasting durability. No assembly required, simply open the box, slide the foundation out and unfold, it will immediately open to the shape of a box spring. Worry free 5-year limited warranty. Another comfort innovation from Zinus. Pioneering comfort.