Auralex SheetBlok- 4' x 10'
"Sheetblok is a dense, limp-mass vinyl material that is about 6dB more effective than solid lead at stopping the transmission of sound. It acts as a thin, dense sound barrier layer in walls, ceilings or floors and is most effective when used as one component of a multi-layered construction scheme. 10' x 4' Black only. 1 Roll/40 ft."