3M Fire Barrier Block B258, Maroon, 2.36 in x 5.12 in x 8 in, 12/Case

• Block is paintable with primer
• Can be repaired and reused as needed, saving time and labor
• Can be sealed with 3M Fire Barrier Rated Foam FIP 1-Step and other 3M fire barrier sealants (sold separately)
• Firestop tested in accordance with ASTM E 814/UL 1479
• Fits medium to large openings in wall and floor through-penetrations
• Installation requires no special tools
• No cure time means faster completion
• Pre-formed foam block maintains tight firestop seal to prevent fire, smoke and toxic gas transmission

3M Fire Barrier Block B258 is a pre-formed foam block designed for easy installation to effectively seal larger openings against smoke, toxic gas and flame. It is simple to use and helps reduce sound transmission.

A Better Way to Fill Large Gaps
When 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 penetrations

Fully Tested and Approved
3M™ 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 Protection
Effective and easy to install, 3M™ Fire Barrier Block B258 are part of our 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.

Trusted 3M Fire Barrier

The 3M Fire Barrier Block B258 offers reliable fire protection with its trusted brand and model. This maroon block is designed to meet demanding firestop requirements, ensuring safety in various settings.

Its proven performance makes it a dependable choice for commercial, industrial, and residential applications, providing peace of mind with every installation.

Exact Dimensions Provided

This fire barrier block measures 2.36 in x 5.12 in x 8 in, giving a precise fit for medium to large openings. These dimensions help technicians quickly fill gaps without guesswork or extra trimming.

With its pre-formed foam design, the block maintains a tight seal to prevent fire, smoke, and toxic gas transmission, enhancing safety where size matters.

Convenient Pack Size

Sold in cases of 12, the 3M Fire Barrier Block B258 offers enough material for multiple installations or larger projects. This pack size helps reduce ordering frequency and keeps job sites stocked.

Having a full case on hand supports efficient workflow, especially when sealing multiple penetrations or large wall and floor openings.

Simple Installation Process

The block requires no special tools and has no cure time, allowing faster completion of firestop sealing tasks. Its paintable surface with primer also helps achieve a seamless appearance after installation.

Technicians can trim the foam easily on site to fit custom openings, and the blocks are reusable, saving time and labor on future repairs or adjustments.

Compatible Sealant Options

After placing the 3M Fire Barrier Block B258, seal around the perimeter with 3M Fire Barrier Rated Foam FIP 1-Step or other 3M fire barrier sealants (sold separately). This ensures a complete firestop system.

The block fits a variety of penetrations including metal pipes, cables, and cable trays, making it versatile for different construction needs while maintaining fire safety standards.