tell me more about this pressure balancer-

[sniggihwerdna]

I'm cleaning out stuff and came across this. I can't recall where it would be used, or what it's called specifically. Help me out please! thx in advance

 

[breplum]

It has a balancing spool inside, which is serviceable. We always install them with shut-offs to make it easy.
It is designed and required to be used on all shower valves that do not have on-board pressure balancing mechanism.