This description covers the sole-source authority allowing agencies to contract without full and open competition when required supplies or services are available from only one responsible source and no other type will satisfy agency requirements; for DoD, NASA, and the Coast Guard, it also applies when only a limited number of responsible sources can satisfy the requirement. It may apply to unsolicited research proposals showing a unique and innovative concept not otherwise available to the Federal Government and not resembling a pending competitive acquisition, or for DoD, NASA, and the Coast Guard, a unique capability to provide the proposed research services. It also may apply to follow-on contracts for continued development or production of a major system or highly specialized equipment—and for DoD, NASA, and the Coast Guard, continued highly specialized services—when competition would cause substantial unrecovered duplication of cost or unacceptable delays. Brand-name descriptions or attributes peculiar to one manufacturer generally prevent full and open competition and should be used only when justified and approved, while brand-name-or-equal descriptions do provide for full and open competition. The cited authority is 10 U.S.C. 3204(a)(1) or 41 U.S.C. 3304(a)(1).