GREAT STUFF PRO Window and Door Polyurethane Foam Sealant is a specially formulated, minimal-expanding foam with a low pressure-build that remains soft and flexible after curing. The foam can be formed without trimming to create a long-lasting, airtight, and water-resistant seal proven not to bow window or door frames when properly installed. Using our GREAT STUFF Contractor Kit is easy. Pop the top off the can, screw it onto the gun, open the gun's valve, pull back the trigger and you are good to go. Still have foam left. Leave the can attached to the gun and close the valve until the next use. Use the cleaner on the outside of the gun and clean the inside when you are going to store it for a longer time. After you use the cleaner, remember to remove the can and empty the cleaner from the gun.