The Great Stuff Pro 14 gun is designed to create an air- and moisture-tight seal between the gun and the can. This prevents the foam from curing and blocking the dispensing valve, letting you reuse the can for up to 30 days. Store can upright with gun securely attached. The gun has a flow control screw mechanism located on the back, which allows you to dispense beads from 1/8" to 3" in size. The nozzle design permits you to place the bead precisely where you want it. One-hand operation eases use in tight spots and hard-to-reach applications. Achieve maximum yield from every can, avoid waste and lower your cost.