This Johns Manville R-13 kraft-faced fiberglass insulation roll (Model# B1284) covers 40 square feet and is designed for use in standard 2x4 wall cavity applications. The kraft facing acts as a vapor retarder and helps with installation. R-13 is one of the most common insulation ratings for interior walls in residential construction and meets building code requirements in most climates. This roll is in like-new, in-box condition and is a cost-effective solution for new builds, renovations, or weatherization projects.