This is the OEM cartridge for Moen's best selling valve, Posi-Temp. You'll generally need a new cartridge if you are experiencing any of the following:
Moen's Posi-Temp valve is very simple and only has this self-contained Posi-Temp Cartridge, held in by a small horseshoe clip.
The best way to identify if you have a Moen Posi Temp valve is to remove the shower handle and escutcheon plate and inspect the valve. The Moen Posi Temp cartridge has a distinct look, and would be hard to mistake for another part, especially if you have removed the cartridge already. Be sure to shut off your Main Water Supply before doing any work on the valve.
It is also important to NOT assume that just because it says Moen on the shower plate that it is a Posi Temp valve. There are several Moen Valves on the market, with distinct parts. You can differentiate between these valves by observing how the water turns on and how the temperature is controlled.
Moen's Posi-Temp Valve turns on by simply rotating the handle counter clockwise. If your shower turns on by pulling out the handle, this IS NOT the cartridge for you and you'll want to refer to the Moen 1225 Cartridge to repair your valve.