Original Resolution: 225x300 1 4 28 Straight Grease Zerk Nipple Fitting 1000 Pcs Taper Thread Ebay A grease fitting, grease nipple, zerk fitting, grease zerk, or alemite fitting is a metal fitting used in mechanical systems to feed lubricants, usually lubricating grease, into a bearing under moderate to high pressure using a grease gun.