RTV foam (two-part, liquid-silicone elastomer). Good for complex through-penetration applications. Re-enterable/repairable. Easily mixed by hand (small amounts) or by automated mixing and dispensing equipment (large amounts).
A two-part, liquid-silicone elastomer that foams in place when mixed. Firestops and seals large and complex penetrations. Cures in 1-5 minutes to form an elastomeric compression seal. No ampacity derating of cables when used properly.