Aero-Tech ULA-100 20,000 Hour 150-Watt A21 Clear Rough Service Incandescent Bulb, 6-Pack 26 times the life of average bulbs saving labor & replacement costs Brass base eliminates corrosion and prevents base from sticking in socket 5 support wires to help provide long life with excellent resistance to vibration and shock Special rare Krypton gas mixture reduces heat and prolongs filament life Made in the USA