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. 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).