This is my no.3 entry and compaired to the other two this one is defferent because i only made modification on the cap adding a ball connected to a steel thin rod that is connected also to the trigger. when the trigger is pushed the ball retracts and lets the sealer flow. when the trigger is released the spring pushes the ball stoping the sealer flow even if there is still some presure left in the tube. also i added a small wiper that wipe's the excess sealer and eliminates the need of using a spatula for a straight finish. All the components i added can easyly be replaced.