These couplings make it easy to rapidly assemble cut lengths of concrete-encased Super Duct. Push the spigot end of the duct into the fitting socket and hammer lightly against a piece of wood located at the end of the coupling or pipe until end of duct butts up against the inside shoulder of the fitting. Push-fit couplings are not watertight and are only recommended for use when encased in concrete. Concrete encased and direct burial applications for power utilities street lighting and communication distribution systems Best when encased in concrete Easy to use Push fit