Even if you performed the world?s greatest door or window installation, there will be gaps around the frame. We?ve got the easy, affordable way to seal those gaps ? GREAT STUFF? Window & Door. It works hard without being hard on surfaces.It expands just enough to fill gaps without bowing or bending the frame, when properly applied and offers greater insulation value than chinked fiberglass or caulk. GREAT STUFF Window & Door forms a durable, airtight and water-resistant seal that can help lower energy bills. One can will fill an average of four to six residential windows.