Draftstop 812 Low Pressure/Non-Rigid Polyurethane Foam is available in 26 oz. gun grade and 16 oz. Stop N Store straw grade canisters. Draftstop 812 is low pressure single component polyurethane foam designed to fill gaps between fenestration products and rough openings. It will provide an airtight seal and protect against water, air and sound intrusion. It is closed cell, minimal expanding foam which will not absorb water, warp or deflect window or door frames.