You are buying a DOZEN brand new Collar Bushings, NSN 3040-01-251-9383. These are seat bushings for M998 HMMWV “Humvee.” AM General p/n 5594001, US Army p/n12338539. These are high quality pieces of hardware, would be great for custom, hot rod, competition or motorcycle applications. They appear very similar to spacers used on motorcycle gauges, fuel tanks, and body panels with a rubber grommet. Other potential uses may be shock absorber, swaybar link, and even accessory installation. O.D. of the bushing is 1 inch. Center hole diameter is 0.3175″, suitable for a 5/16 bolt. O.D. of the stepped collar is 0.45″, between 7/16 and 1/2 inch. Total height of the bushing is .540″. Original invoice on these is $5.49 each, Get a dozen here and save some $$$$, we ship fast and free too! 15057 L4A1