This requirement is for a quantity of 4 units of a specific NSN item, with delivery FOB origin. Acquisition is restricted to government-approved sources because the item is flight critical and requires engineering source approval; detailed technical data is not available for full competition. New sources must submit all required source approval information per the NAVSUP WSS brochures, and offers lacking complete data will not be considered. Approval of a new source typically cannot be completed in time to delay award, so only previously approved sources are solicited. The government is not using commercial item acquisition procedures for this procurement.