Boss 143137 24 oz 338 Flexible Foam Gun Grade - This is a unique, flexible, minimal expansion, one component, moisture curing PU foam. It is designed for window and door installs, insulating wall panels, electrical outlets, pipes and vents. It has a very high elastic recovery (up to 90% if compressed by 75%). It features excellent adhesion to almost all substrates as well as excellent thermal and acoustical insulation.