Our synthetic roof underlayment is 10x stronger than #15 felt. It can withstand higher wind conditions preventing blow offs & tears. Non-slip foot traction results in safer installs especially on steep slope roofs & windy weather. Proprietary formulated anti-skid bottom coating to prevent underlayment slipping & shifting. Will not absorb moisture, become brittle in cold or leach oil over life. 100% recyclable, containing post-industrial recycled polymers & impervious to mold growth