Helpful hint. If you are trying to replace a Moen 1222 tub/shower cartridge from an older valve, you will pull the cartridge out and see o-rings on the front and backside of cartridge. The newer Moen 1222 cartridges have only one o-ring on the front side. You may have problems trying to get the retainer clip back in upon replacement of new cartridge. You will see that the new cartridge is about 1/16" longer if you compare side by side, and you will fight trying to put the retainer clip back in. To resolve issue, you want to slightly bevel the outer back edge of the plastic cartridge. (The inside circular perimeter of the old brass valve isn't perfectly flat on the inside edges). By beveling the plastic backside edges, it will push in the little tiny bit you will need to get the retainer clip back in. It will not harm anything by doing so. Hope this helps someone, as I saw a thread in regards to this issue.