APOC 36 in. x 144 ft. 432 sq. ft. Felt Roof Underlayment AP-0042 - The Home Depot
QuietWalk Laminate and Hardwood Acoustical and Vapor Barrier 33.34-ft x 3-mm Premium Felt Flooring Underlayment (100-sq ft / (Roll) in the Flooring Underlayment department at Lowes.com
Epilay® Plasfelt™ 36-in X 144-ft 432-sq Ft Felt Roof Underlayment - Fort Mitchell, AL - Fort Mitchell Trading Post & Hardware
ROBERTS Super Felt Underlayment - 100 sq. ft. Roll - 44" x 27.3' x 3 mm - Carpet Underlayments - Amazon.com