This is a sole-source procurement for four flight-critical parts, where only previously government-approved sources are being solicited. The government lacks sufficient technical data to conduct a full and open competition for this item. Unapproved sources may submit a proposal but must include a complete source approval request, with the understanding that the approval process is lengthy and may preclude award if it cannot be completed in time to meet the government's needs. The performance location is not specified. Budget information is not provided.