It's a larger duplexer than that, about 7x9 inches overall size, with N connectors.
I know, LMR isn't optimal for this application but it's not expensive and is easy to work with and is the de facto standard
for lower cost radio installations, at least in central florida. It's almost rare to find anything else in use.
I don't spec what goes in, that's not my job. I maintain and install what I'm told to maintain and install.
If it were my job to spec out systems, I'd be trying my best to sell better products and systems to my customers.
But this is lowest competent bidder work. Keep that in mind. The safety of your kids at school may depend on the
performance of repeaters and portable radios that were selected because of LOW COST. Feel better now?
And I've got to make it run right when it misbehaves...and its normal state of operation is never all THAT far from misbehaving.