need to increase from 5 to 6". Is a reducer/increaser the same thing (just flip it over?) or does one end of it (which end?) need to be crimped? I see some specifically called reducer or increaser, then I see some "increaser/reducer' meaning you can just flip it over! Then some have a crimped end - and others don't. Is a crimp required? up end or down end? what is the purpose?