Although “caulk” and “sealant” are often used interchangeably, a sealant is generally a high-performance caulk. A product that meets or exceeds the requirements of American Society of Testing Materials (ASTM) Specification C-920 is considered a sealant because of its high-performance characteristics, such as durability both inside and outside and during inclement conditions. If there are no specifications on the label—or if the label says the product meets requirements of ASTM Specification C-834—it is considered a caulk.