Traditional mattresses are made of coils of wire springs known as inner springs and they are surrounded by layers of foam and fabric to provide cushioning. In a double sided mattress, the layers of foam and fabric are evenly distributed on both sides of the inner springs. In the single-sided mattress, all the "comfort layers" are put on one side of the inner springs. Most of the mattresses sold today are single-sided. Most major manufacturers changed to single-sided mattresses when new governmental regulations were passed in 2007. It became too expensive to comply with flammability regulations for both sides of the bedding. There are some smaller companies like Englander and Campbell Mattress Company that continue to make double-sided mattresses. And some of the major companies still make them for their hotel clients.