After 5 million slam cycles under the Window & Door Manufacturers Association NWWDA T.M.7-90 cycle-slam testing protocol, the SL-17 FRP (Fiberglass Reinforced Polyester) Flush Door showed no operational damage or hinge separation. Made with stiles and rails of extruded 6063-T5 aluminum alloy for strength without bulk. Less door mass means reduced wear and tear on hardware and framing for longer system life and less effort to open. Poured-in-place urethane core bonds to internal structural elements to create a solid, completely sealed unit with impact resistance, flexural strength and minimum R-value of 3.45. Unlike metal or wood doors, SL-17 doors never rust, corrode, crack, split, peel or rot, and retain good looks for years with only routine cleaning using mild soap and water. Greenguard Indoor Air Quality certified, including stringent Greenguard Standard for Children and Schools. Made to order as large as 80 ins. wide by 216 ins. tall and in configurations such as arched doors and transoms, unequal pairs, dutch, bi-fold and odd sizes. For schools, public buildings and other facilities. Special-Lite Inc., Decatur, Mich.