You know you're interested in substitutions. Designers want to avoid them and contractors want to make them. But what's an option? You need to read the bidding documents and specifications carefully to understand exactly what is required and what is permitted in the particular contract you are working with.
"A substitution request is a proposal to use a manufacturer, product, material, or system different from one required in the contract documents," begins the chapter on substitutions in the Fundamentals and Formats module of the CSI Manual of Practice (MOP). An option is one of several manufacturers, products, materials, or systems, permitted for a particular purpose or location in the contract documents. And what are the rules for requesting substitutions? They vary from one contract to another.