What connects couplings of different sizes together?

Adapters are specifically designed to connect couplings of different sizes together. They serve a crucial role in fire service operations, allowing firefighters to utilize hoses and connections that may not be the same diameter. By inserting an adapter, the compatibility between different equipment is achieved, ensuring that water can flow seamlessly from one hose or fitting to another, regardless of size discrepancies.

While reducers and fittings also serve important functions, their roles are more specialized. Reducers specifically transition between larger and smaller connections but do not generally connect two different sized couplings. Fittings, on the other hand, are a broader category of components used to connect or modify the path of piping and tubing, not necessarily focusing on size differences. Connectors can refer to various types of joiners, but they do not specifically denote the size adaptations typically addressed by adapters. Thus, adapters are the correct choice for this specific need.