"The concave steel wood burning fire pit is designed with a distinctively curved construction that combines modernism and casual elegance with a clean, streamlined, elegantly simple silhouette creating unparalleled beauty in any outdoor destination. 17 Stories manufactures and utilizes industrial-strength tank heads for the bowls used in their fire pits. Tank heads are the end caps on cylindrically shaped pressure vessels. They generally comply with ASME standards because of the high pressures they must withstand for use with gas storage tanks and reactors.