These primers (not a sealant by itself) are designed to be used on stainless or galvanized steel (not required on brass) or in applications where a rapid cure time is required (such as in a cold environment or where the fitting is being installed quickly). Clean and dry thread surfaces and then apply the primer. Allow to dry for 10 seconds and then apply the appropriate sealant. Contains no ozone depleting compounds and is NSF-61 certified. The Loctite N7649 is the standard primer with a copper content, and the Loctite T7471 has no copper content and is a "delayed" organic accelerator (accelerates cure after being assembled for 5 minutes). MSDS sheets are available at new-line.com.