Metacaulk® Putty Pads are used to maintain the hourly rating of fire rated walls containing electrical outlet boxes and to reduce sound transmission. Only one pad thickness (1/8) inch is required for a 1 or 2 hour fire rating. No additional putty material is needed to plug the end of each electrical metallic tube or conduit at its connection to the box. Sound Transmission Class (STC) Rating 60*. *Tested in a UL 411 wall assembly/section to ASTM E90.