NW Wood 540 is the slimmest wood frame in the folding door industry. With a quadruple laminated cross-grained wood frame profile styled in a subtly rounded design, the intersection of two folding panels is a mere 5 11/16″ (144 mm). NW Wood 540 is built with solid premium wood to achieve the tall, slim-framed panel design of this fourth generation wood system. All panel sizes and configurations is Florida statewide approved with Product Approval number FL41107. Depending on glass type selection, NW Wood 540 offers exceptional thermal performance values as low as “.19”.