ProArmor Synthetic Roof Underlayment with Fusion Back Coating Technology is strong, durable and repels water. Its also light, easy to install and contributes to safe working conditions. In addition to its unparalleled quality and performance, ProArmor Underlayment offers the following features and benefits. 10 square rolls provide more coverage compared to felt paper. Lightweight and easy to install with nailing guide. Dual-surface slip resistance: fusion back coating technology paired with a non-woven surface provides excellent walking conditions during shingle application even on steeply pitched roofs.