Which type of fitting is known for its ability to be easily connected and disconnected?

The type of fitting that is known for its ability to be easily connected and disconnected is the union. Unions are designed specifically to make it simple to connect two pieces of pipe or tubing and allow for easy disassembly without needing to cut the piping systems. This feature is particularly beneficial in systems that may require frequent maintenance or changes, as unions provide a reliable and straightforward way to separate components without compromising the integrity of the system.

In contrast, other fittings like couplings serve to connect two pipes but generally do not allow for easy disconnection without cutting or damaging the pipes. Elbows are used to change the direction of the piping but do not facilitate disconnection, while crosses connect four pipes at a junction, which does not simplify the process of connecting or disconnecting individual sections.