Hey guys! I think this might be my first post. It's good to be here. Well, let's get down to business. I have a leak under my kitchen sink. There is a little 'black locking ring' that like tightens around the piece of PVC as it comes out of the base of the sink. Here is an image of it. http://imgur.com/a/uIcU5 Well, the smaller of those two black rings has a deep crack in it. So it doesn't create a seal and the water leaks out of it. I have a bucket underneath that pipe, although the photograph doesn't show it. My question is, what is the name of that 'black locking-ring' that tightens around the PVC? I want to go to Home Depot and pick up a new one but, I'm not sure what the part is called. Any ideas?