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. STC rating 60*. *Tested in a UL 411 wall assembly/section to ASTM E90.