? 12-Inch Female-Female Hose - What For?

Water filter.

To connect your sewer line to a Barker Tote tank use a garden hose.
You will also need a twist on sewer cap with a built in hose connection on your RV.

I have no idea what you use yours for but I have one at my ranch in case my well goes out. I can connect my water faucet to my neighbors water faucet to get water to my house

The connection on my black tank flush has a female connection. I don’t think I’ve ever seen a male connection on the flush connect. What I think, is that that small piece of hose fits between the water source and the porta-tote connection to rinse out the tote after dumping. On my tote, there is a connection that serves there functions. 1) has a red plastic pop-up to indicate when the tote is full. 2) an air vent to allow air in as stuff goes out. 3) serves as the flush connection. I lost mine so if the OP would like to get rid of it, PM me.

the title of this thread took me somewhere else.............

likely to flush the black tank?

Usually used on your black tank flush in your wet bay.

Came with a water filled.

The same piece like that that I have came with a hose reel for connecting to the water source.

Because you have a section of hose with male connections on both ends?

Hook up your hose reel to another hose or the faucet.