3M Fire Barrier Moldable Putty Stix MP+ Red – Intumescent Firestop, Re-Enterable, 1.45 in x 6 in

3M Fire Barrier Moldable Putty Stix MP+ is designed for professional firestop work. This one-part, re-enterable intumescent putty can be shaped to fit through penetrations and blank openings in fire-rated assemblies. Its dark red color helps you visually confirm coverage and edges as you work.

What it does

The MP+ putty sticks provide a customizable seal that forms a protective barrier when exposed to heat. It remains workable over time, so you can adjust, re-enter, or repair the seal without crumbling.

• Tested performance up to 4 hours per ASTM E814 (UL 1479) and CAN/ULC S115, giving you documented firestop capacity.
• STC 56 rating in compatible wall assemblies, supporting sound isolation alongside fire protection.

In addition to fire protection, the putty creates a draft and cold smoke seal, helping minimize unwanted air leakage and smoke migration around openings. It is noncorrosive and compatible with metal, as well as synthetic cable jackets, which can simplify installation in mixed material environments.

Ease of use and durability

• One-part, ready-to-use, re-enterable putty that can be molded to fit irregular openings and penetrations—no mixing required.
• Remains workable over time and will not dry out or crumble, enabling re-entry for inspections or adjustments.

Typical use cases include sealing around electrical conduits, plumbing penetrations, and cable bundles within fire-rated walls and floors. The color and finish make it clear where the seal is applied, while the compact dimensions (1.45 in x 6 in) keep it manageable for field work.

Note: This product is intended for industrial/occupational use and is not sold for consumer retail. When used as part of a tested system, MP+ helps support compliance with firestop and sound ratings while providing a practical, rework-friendly solution for installers.