It looks like 2112 is a Moen single handle shower system that uses the Moen Posi-Temp valve. I replaced some Posi-Temp valves in my showers, and it was pretty easy. The newer ones are brass and plastic, and seem to be working just as well as all the old all- brass ones. https://www.lowes.com/pd/Moen-1-Handle-Brass-and-Plastic-Faucet-Tub-Shower-Cartridge/3133585 ? They usually come with a crappy plastic faucet puller, but I spent the $16 on a metal tool to get the old cartridge out and put the new one in. It helped out a lot!! The old ones can be tough to wiggle out, and this was the right tool for the job: https://www.lowes.com/pd/Danco-Cartridge-Puller-For-Moen/1085199 Answer from GarthFranklandOates on reddit.com