The retractable roof at the University of Phoenix Stadium is comprised of two 180-feet long by 240-feet wide retractable panels that will remain closed to allow for air conditioning during the hot summer months and then open during the cooler months to take advantage of the Valley's abundant sunshine. The fabric roof will allow light to fill the stadium and provide an open, airy feel even when the roof panels are closed. The roof system is designed to close in approximately 12 minutes. University of Phoenix Stadium features a unique rollout natural-grass playing field, contained in a single tray measuring 234 feet wide by 403 feet long and weighing a hefty 18.9 million pounds. The first completely retractable field in North America, it will be positioned inside the stadium on game days to offer the preferred natural-grass playing surface for football and outside the stadium the remaining 350+ days of the year to receive the needed sunlight and water to grow. A total of 462 steel wheels riding on 13 parallel steel rails are used to slide the field tray in and out of the facility.