Johns Manville Formaldehyde-free Kraft-faced fiberglass rolls are for use in 2' x 4' stud wall cavities with 16" on center spacing (exterior sidewalls, basement walls and garage walls). Kraft facing serves as a vapor barrier to help manage moisture and includes tabs for easy stapling to wood framing. This product helps save energy and provides good sound absorption. The glass fiber will not settle rot, mildew or deteriorate and rolls can be cut to any length. This product has been GREENGUARD® certified for superior indoor air quality.