Lumax LX-3401 Gold/Silver Spin Drive/Self Tapping 1/4"-28 Special Taper Drive Thread Straight 0.57" Long Grease Fitting, (Pack of 100) Thread forming, spin drive, fittings Passivated finish for maximum protection from corrosion Heavier wall thickness for extra strength Stress relieved and tempered carbon steel spring Ball check in head prevents dirt from getting in