Difference between a fitting reducer and a reducer coupling?

[gblades]

What is the difference between a fitting reducer and a reducer coupling.

Take for example one which is 15mm one end as 10mm the other.
I am guessing a reducer coupling solders over the top of a 15mm pipe one end and a 10mm pipe the other.
Then a fitting reducer would effectivly be a 15mm pipe one end and a 10mm pipe the other?

So if I had a 15mm isplator that I wanted to connect a 10mm pipe to the best method would be to use a fitting reducer to connect directly to the isolator and then the other end would be joined to the pipe with a straight 10mm solder coupling correct?

Thanks

 

[kirkgas]

your description seems right as you can get internal and external reducers, (ie the 15mm end either goes in a fitting or over the pipe, with the 10mm end going over the pipe) so you need to buy exactly what you need

 

[doitall]

A YP 6 fitting reducer, reduces the fitting.

A YP 1r reducing socket, reduces the pipe.