REX™ SynFelt is constructed of a high strength woven fabric coated on both sides with a specially formulated anti-slip walking surface and is 100% asphalt free. REX™ SynFelt is 7 times lighter and 20 times stronger than 30# asphalt felt paper and comes 10 squares to a roll offering far more coverage per roll. With a patent pending special preprinted nailing pattern, the REX™ SynFelt underlayment provides easy installation providing you with cost savings.