QuietPutty is Class-A fire-resistant acoustical putty designed to preserve the performance of STC rated assemblies. We use QuietPutty on electrical outlet boxes, rocker switches, HVAC ducts, water hookups, cable systems or any other penetration that require an acoustic seal. QuietPutty will not shrink and remains soft over time, ensuring a long-term seal that maximizes STC performance. We use QuietPutty with QuietRock sound reducing drywall and QuietSeal Pro acoustic caulk - the complete Quiet® Sound Damping System - for reliable, low cost results.