ALCO SHIELD is a fiberglass reinforced, polymer modified asphalt membrane used as a shingle underlayment for sloped roofs comes with either a smooth or granular surface. It resists the penetration of water due to wind and rain or ice dam back up. ALCO SHIELD also comes in a HI TEMP version for under metal tested for up to 240 degrees. For more information, visit www.alconvc.com.