Lennox 18D42 - Boss 12501, Multi-Seal 125 Building/Construction Sealant, White, 10 Ounce Cartridge

 

Lennox 18D42 – Boss 12501 Multi-Seal 125 Building & Construction Sealant is a professional-grade, multi-purpose sealant designed for durable sealing in HVAC, construction, and general building applications. This high-performance white sealant is formulated to provide long-lasting flexibility, strong adhesion, and reliable weather resistance on a wide range of common building materials.

Multi-Seal 125 is ideal for sealing joints, seams, penetrations, and gaps where air, moisture, dust, or vibration may be present. Its non-sag consistency allows for clean vertical and horizontal application, making it suitable for both interior and exterior use. Once cured, it remains flexible to accommodate normal expansion and contraction without cracking or shrinking.

Commonly used by HVAC technicians, contractors, and maintenance professionals, Lennox 18D42 Boss 12501 helps improve system efficiency and protect building components by creating a tight, durable seal in demanding environments.

 

Product features and benefits

• Professional-grade building and construction sealant
• Strong adhesion to metal, masonry, wood, plastic, and other common substrates
• Flexible cure resists cracking from movement and vibration
• Weather-resistant for indoor and outdoor applications
• Non-sag formula for vertical and overhead joints
• Clean white finish for a professional appearance

 

Applications

• HVAC ductwork and cabinet sealing
• Wall, roof, and panel joints
• Penetrations around piping and conduit
• General construction, repair, and maintenance sealing

 

Specifications

• Lennox part number: 18D42
• Manufacturer part number: Boss 12501
• Product type: Multi-purpose building and construction sealant
• Color: White
• Package size: 10 ounce cartridge
• Application method: Standard caulking gun

 

Lennox 18D42 Boss 12501 Multi-Seal 125 is a dependable sealing solution for contractors and technicians who require consistent performance, strong adhesion, and long service life in professional building and HVAC installations.