A Better Way to Fill Large GapsWhen sealing larger cavities, use 3M Fire Barrier Block B258 to restore the integrity of the wall with a simple "stack, seal, and done" application, without the use of special tools. The blocks are engineered to remain securely in place, eliminating traditional wire mesh reinforcements. Pre-formed blocks help technicians fill large openings quickly. The material is easy to trim on site without special tools, achieving a tight, custom fit. No cure time is required, which means installation is completed faster, and the blocks are paintable with primer for a more seamless appearance.The blocks are fully re-enterable and reusable, saving time and money, while minimizing waste. Once the opening is filled, seal around the perimeter and any penetrating items with 3M Fire Barrier Rated Foam FIP 1-Step or other 3M fire barrier sealants (sold separately).Recommended Applications Blank openings Metal pipes Cables Cable trays Insulated pipes, combination penetrationsFully Tested and Approved3M B258 Fire Barrier Blocks are firestop tested to the criteria of ASTM E 814/UL 1479 Standard Test Method for Fire Tests of Penetration Firestop Systems, ASTM E 84/UL 273 Standard Test Method for Surface Burning Characteristics of Building Materials, ASTM E 90 Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements, and ASTM E 413 Classification for Rating Sound Insulation.Reliable and Affordable Fire ProtectionEffective and easy to install, 3M Fire Barrier Block B258 are part of 3M's family of fire protection products that offer the broadest, long-lasting solutions for a variety of commercial, industrial and residential applications. As a trusted leader in the fire protection industry, 3M offers a broad line of affordable products designed to meet the most demanding firestop requirements. Find the solution you need from the industry-preferred line of fire protection products.