WaterWay Rainscreen Mats use a proprietary filter fabric that performs like an extra layer of housewrap. This material surpasses water hold-out requirements for weather resistive barriers and offers a perm rating of 247. The rainscreens create space for continuous ventilation and drain water faster than normal stone installations. Stuc-O-Flex International Inc. 800-305-1045. www.stucoflex.com