Special Notice: DEPT OF DEFENSE, DEPT OF THE AIR FORCE is procuring BACK-UP RING, PREFOR (NSN: 5330-01-647-9819) under the category of PACKING AND GASKET MATERIALS (PSC code: 5330).
A BACK-UP RING, PREFOR is typically used as a sealing component in various applications to prevent leakage and maintain pressure integrity.
Please ensure a concise and accurate summary to avoid any negative consequences.