On federal work this falls under FAR 11.105, "Items Peculiar to One Manufacturer." The agency must document, in writing, why no other product will meet the actual need before it can restrict a specification to one source. State and local agencies typically mirror this with their own justification and disclosure requirements. Many require the sole-source designation to be published with a window for another vendor to object before it stands. Sole source sits at the far end of a spectrum from approved equal (fully competitive) and basis of design (defaults to one product but still allows an equal). A sole-source spec does not allow substitution. Sole-source language is useful to catch early in project qualification. It usually signals the commercial outcome is already decided. Nonlinear flags sole-source and brand-restriction clauses as it reads a bid package. A contractor or supplier can avoid spending estimating hours on a bid that was never open. The manufacturer already named can see where they are protected.
Knowledge Base
What is a sole-source specification?
A sole-source specification names one manufacturer's product and gives contractors no path to substitute. It is used when only one product can genuinely meet a documented need, and treated as the least competitive way to describe what an agency wants to buy.
