Hercules® Plumbers Caulk™ is a commercial-grade, easy-to-use, single component, siliconized acrylic-latex non-sag caulk. It forms a flexible, durable, mildew and UV-resistant waterproof seal on interior and exterior surfaces. It flows easily and does not harden in the tube or cartridge, and will not crumble and resists shrinkage. Tack free in 1 hour. Behold the power of Hercules®, products built to last and trusted by plumbers to withstand even the toughest conditions.