The grade F1 white adhesive-backed pressed wool felt strip meets Society of Automotive Engineers (SAE) J314 standards and is an extra-firm fabric commonly used for sealing, cushioning, polishing, and wicking. The grade F1 is made of minimum 95% wool, which provides better insulating properties and a greater ability to absorb and retain water, oils, and other liquids than felt with lower wool content. Its density helps provide high resistance to abrasion and wear, with high vibration absorption. The strip has an adhesive backing for surface mounting and is rated for use in temperatures ranging from 0 to 180 degrees F.

Felt is a fabric made from interlocking organic or synthetic fibers. It is often made of wool because of the fiber€s ability to absorb and retain moisture and to provide thermal insulation, but it can also be made of synthetic materials such as polypropylene and polyester. Pressed felt is produced by wetting and agitating wool to form connecting fibers. Needled felt is produced by a dry process of vertically needling fibers together and is typically used for synthetic materials. The higher the tensile strength, the more the felt is able to resist stress and deformation. Firmness is measured by pounds per square inch (psi) of pressure to achieve 10% deflection.