If you call Delta, I think they'll help you identify it, and, they'll send you the parts for free. It looks like the one I installed at my mother's house, but I do not remember the number. The nice thing about Delta, is that they do not use that many different pieces, and it should not be hard for them to help you out. If it's the one I think you have, you'll need something with a small hook on it to pop out the gasket seal in the back - I used a piece of copper wire. You do not want to scratch the housing, but the whole thing should only take a few minutes to fix. I will say that you may want to have some silicon plumber's grease on hand, otherwise, some people may have difficulty pushing the new one in. Swipe a small amount all around the O-ring, and it will pop right in, otherwise, be prepared to push!