The Government requires spare parts that are form, fit, and functionally interchangeable with those currently used on the supported end item or weapon system. The acquisition is restricted to the foll... The Government requires spare parts that are form, fit, and functionally interchangeable with those currently used on the supported end item or weapon system. The acquisition is restricted to the following source(s) of supply, which are the only source(s) known to have the capability of furnishing the required supplies and the only source(s) currently approved by the design control activity.