Boss 146818 334 Minimal Expanding Foam Genius Gun - BOSS® 334 Genius Gun® Window & Door Minimal Expanding Foam is a one-component, ready to use polyurethane foam, formulated to seal the gap around window and door frame and the rough opening. BOSS® 334 expands to generate an effective seal, and when used properly is proven not to distort or bow window and door frames. BOSS® 334 will achieve a Sound Transmission Class (STC) of 58 when applying it in accordance with ASTM C-919.