In contrast, closed specifications restrict the bidder, in varying degrees, as to which products, materials or means can be used.
Less restrictive, closed specifications, which include a list of adequate substitutions, often are referred to as bidder's choice.
limit the contractor's choice of methods and materials.
Since there is a suggestion of discrimination when only one supply source can be used, closed specifications
are not common in public contracts.
Closed specifications contain specific descriptions; for example, a lamp standard of a specific manufacturer and a specific model number.
One advantage of using closed specifications is that the specification writer can precisely and easily describe the standard wanted.