There are two types of connectors. One is used only for buried work and the other can be for either above ground or below. Both of these come with models that will match the different pipe materials such as PVC to CI, PVC to PVC, etc.. The underground type is just a neoprene sleeve with a stainless steel clamp on each end. These are often called, "Ferncos", but that is a brand name. The other type is called a banded coupler or no-hub. These also have a sleeve, but the band covers the entire sleeve. These offer a ridged joint when not supported by earth. Use the type that is designed for your application. I have not idea of the cost, but that is not important if you have to make this transition. Would you save by ordering on-line or by mail. I seriously doubt it. Even the the unit price was considerably less, the shipping charge would eat that up and more. Also, if you deal locally and the coupler isn't the right one, you can take it back and get a different one. Exchange with an on-line seller will usually cost a restocking fee, you will have to pay return shipping as well as the shipping for the new part. Not too good of an idea.