Specifications include, but are not limited to: Spring Unit: Spring unit is Bonnell 336 coil type construction, thirteen (13) gauge steel spring wire (stressed), six and three-quarter (6-3/4”) high, with 6 gauge border rod around the entire unit. The spring has at least six (6) convolutions to the coil. The twin XL size (38” x 80”) shall have a proportion number of coils, but not less than two hundred sixty (260) coils. The coils shall be joined and secured with cross helicals of no less than seventeen and one-half (17-1/2) gauge wire with ends securely clinched. There shall be a border wire of six (6) gauge both sides, and be fastened by clips securing each perimeter coil to the border rod. The perimeter has a U-Guard placed on every second (2nd) coil around the entire perimeter to ensure firm and durable edges. Upholstery: Both sides of the spring are covered with a ½” fiber insulator pad rated at 2 ounces.