What does this molding actually do? In addition to adding an aesthetic dimension to your baseboards, it actually serves a practical purpose. It protects your baseboards from being chipped and dented by vacuum cleaners, furniture and other things that move around at floor level. Which is why after a few years this molding tends to get a little beaten up.
Typically this base molding comes in 2 shapes, quarter round or shoe molding. When you shop for materials for this project, it is usually best to replace your existing molding with the same shape. Otherwise you may end up having to do a little work on your baseboard or floor to finish previously unexposed areas.
Another consideration is the type of wood. You can usually get pine or oak in both shapes. We recommend that you match your flooring material and that you put a clear or stained finish on the molding as opposed to painting it to match the baseboard. When paint gets chipped off, it can be a lot more conspicuous.