RectorSeal Duct Seal Compound is a gray, soft, non-toxic, putty-type compound that adheres to most clean dry surfaces. Duct Seal Compound is asbestos-free; it will not damage plastic materials, corrode metals, or have adverse effect on human skin.
 
Features
Can be hand applied from 25°F to 120°F
Air/water-tight seal
Resistant to water, alcohols, mild acids & bases
Non-corrosive / non-irritant