The spec names one product as the basis of design. The drawings are built around its size, weight and connections. Other listed manufacturers may bid, but their product must meet the same requirements.
Example: a spec names one manufacturer's ceiling-suspended basketball backstop as the basis of design. The structural drawings show attachment points for that model.
If you bid a different product, compare it to the basis of design line by line. Check size, capacity, finish and warranty. If your product changes structure, power or clearances, say so in your proposal. The spec may make you pay for those changes.