Flex Caulk Pro Series Gutter Sealant seals and bonds all gutter connections in new or damaged gutters. It's a high-performance, hybrid polymer caulk, delivered through our Adjustable Trigger Flow Nozzle, which eliminates the need for a caulking gun and allows you to control the flow of caulk. Just adjust the flow setting and push the trigger for a perfect bead. And when you stop, it stops. There's no running, no dripping, and no mess. No Caulking Gun Needed - Easy To Use.