Foam Gap Filler and Fire Seal

Great Stuff Pro Gaps & Cracks (and Fire block)

Foam Great Stuff Pro Gaps Cracks

http://www.amazon.com/Dow-Great-Stuff-Cracks-341557/dp/B0013WME6C $8.99 + $4.50 shipping

http://www.homedepot.com/p/GREAT-STUFF-PRO-24-oz-Gaps-and-Cracks-Insulating-Foam-Sealant-341557/202892471 $12.47

I use three different types of foam depending on how much expansion I want...
    No expansion - Foam Adhesive
    Small expansion - Foam Windows and Doors
    Large expansion (and fire seal) - Foam Gap Filler and Fire Seal

This is for use with a Foam Gun .
You also need Foam Gun Cleaner .

http://greatstuff.dow.com/products/pro/gaps-and-cracks/

GREAT STUFF PRO™ Gaps & Cracks - As the first foam sealant to be recognized as a fireblock, GREAT STUFF PRO™ Gaps & Cracks inhibits the spread of flames through concealed spaces. It’s a minimal-expanding, single component polyurethane foam sealant for general purpose building envelope air sealing.