Designed for high heel and high r-value roof applications, for either blown-in or batting type insulation. Like all AccuVent versions it is effective in preventing damaging ice damming as well as the growth of mold and mildew. 100% recycled flame retardant plastic meets the new EnergyStar Thermal Bypass Checklist requirement. Available Sizes: 14.5" x 41" & 22.5"x 41"