Johns Manville's Linacoustic® R-300 is a rigid fiberglass board that is specifically designed for lining HVAC plenums and air distribution ductwork, and meets or exceeds all ASTM C 1071 Type II duct liner requirements. Linacoustic R-300’s airstream surface is coated with our proprietary Permacote® coating, which provides a durable and smooth surface that is resistant to the accumulation of dust and dirt. It also provides added product protection against microbial growth. Linacoustic R-300 provides exceptional durability and superior thermal and acoustical performance to help you create more comfortable and energy efficient indoor environments for commercial and residential building occupants.