3M B258 Fire Barrier Block 8x5.12x2in 2hr Fire Rating Firestop

The 3M Fire Barrier Block B258 (3M part 5078BA) is a pre-formed, elastomeric firestop block engineered to seal openings in fire-rated wall and floor assemblies where cable bundles, conduit, or pipes penetrate the barrier. The block achieves a 2-hour fire rating per UL 1479 (ASTM E814) when installed per 3M's published system designs, intumescing upon exposure to heat to expand and seal the penetration against flame, smoke, and hot gases. Measuring 8 in. long × 5.12 in. wide × 2 in. thick, the B258 block is composed of a graphite-based intumescent elastomer that remains flexible at ambient temperature for easy field fitting and cutting, and requires no adhesive or mechanical fastener for many standard installations. This unit is new, still in original factory plastic wrap, with no signs of use, damage, or prior installation.

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