What type of fitting is used to connect hoses of the same diameter but with different threads?

The correct fitting used to connect hoses of the same diameter but with different threads is the adaptor. An adaptor serves as a bridging tool that allows for the compatibility between two different threading systems while maintaining the same diameter, ensuring a secure and functional connection. This is essential in firefighting scenarios where standardization of equipment may vary between different departments or manufacturers.

In contrast, a hose clamp is typically utilized to secure a hose to a fitting rather than join hoses with differing threads. A reducer is designed specifically to reduce the diameter of the hose, which does not align with the needs of connecting hoses of the same size. Lastly, a gate valve is used for controlling the flow of water within a pipe system, rather than connecting hoses. Thus, the adaptor is the most suitable choice for this particular scenario.