#1 - Hardening

Loctite Gasket Sealant 1 is a solvent based, reliable, paste-like gasket sealant, dressing, and coating. Sets quickly to a hard set and is recommended for rigid, permanent assemblies. Use to 400°F. Resistant to gasoline and other solvents. Applications include threaded connections, air ducts, plumbing connections. For extended gasket life, fast drying, rigid cure. 

#2 - Non-Hardening

LOCTITE® gasket sealant solvent-based, paste-like sealant that sets more slowly to a pliable film and is best suited for nonrigid, vibrating assemblies. Resistant to gasoline and other solvents.

515 Flange Sealant is a flexible, gasketing material for use on rigid machined flanges with less than 0.015" gap. Flexes with flanges that move in service. OEM approved – use where OEs specify 515 or “anaerobic” gasket (cures in absence of air). Eliminates preformed, pre-cut, paper, rubber and cork gaskets.