I would make a list of the essential parts that you need and the non-essential parts. Make sure all of the parts are included in your application but you only want to include the essential items in your claims.
The good news is that usually things like sizes, shaped, or dimensions are not going to limit you (unless you specifically claim them) so if your invention needs a "basin" by all means include the basin in your claims and you should get broad enough coverage on the basin to cover all equivalent sizes and shapes for a basin.