If you plan to supply your own fixtures for a plumbing project, discuss the brand or product line that you plan to use with your plumbing contractor. Many brands have specialized installation requirements and it is a good idea to make sure, up front, that your plumber is capable of dealing with those specialized requirements.
When signing a contract with a plumbing contractor, make sure that model numbers are clearly indicated on the contract for all fixtures to be installed. This way, if the wrong fixture is installed, it will be easier to assign responsibility.