Boss 144150 Plastic Tip Compact Applicator Gun for 334 Expanding Foam - This plastic tip compact applicator gun is for use with the BOSS® 334 Expanding Foam. The expanding foam is used in conjunction with the applicator gun to properly apply the solution to window frames, door frames, roof applications and more. Please note that this is the applicator gun only. The BOSS® 334 Expanding Foam is sold separately.