RectorSeal No. 5 is our most popular thread sealant. It has withstood the test of time in a variety of uses and is widely known as the "standard of the industry." RectorSeal No. 5 is a soft-setting, slow-drying thread sealant made from special inert fillers dispersed in an oleoresinous base to facilitate its application to threaded pipe connections. RectorSeal No. 5 is a unique, versatile and reliable sealant that is non-toxic in accordance with NSF Standard 61-G & 372. In addition, it is Underwriters Laboratories Inc. (UL) classified, listed under the Uniform Plumbing Code (IAPMO) File No. 1282, and it is approved and listed with the Canadian Standards Association (CSA).