S18105 Limestone Vulkem 116 caulk is used for a wide range of pool and spa repair. One of the main uses is to securely affix pool tiles together, as well as filling gaps and cracks as needed. Flexible and watertight, caulk is resistant to water damage and mildew. Caulk cartridges require a caulk gun to use, while a squeeze tube can be operated by hand.