A replacement for #15 or #30 oil saturated felt; designed for steep slope roofing under asphalt shingles, synthetic shingles, residential metal roofing and cedar shakes; 12 times stronger than #30 felt; meets and exceeds ASTM D226 Types I & II and D4689 Types II & IV; 8 square more per roll compared to #30 felt; easier to install - wider, lighter and more coverage per lap; synthetic construction is impervious to mold; lays flat and does not absorb water and wrinkle; enhancedUV protection; no oil leaching, no hazardous material content; fiber grip slip-resistant walking surface; advanced backside non-slip coating; low temperature flexibility. Roll size: 10 sq. or 93m .