SmartDrive compact LED bulbs are energy efficient, long lasting, replacements for downlight applications that previously used 4-pin CFL lamps. Keystone's 4-pin LED bulbs provide 50% energy savings when compared to a typical CFL fixture and have 4X the useful life. Keystone makes installing the compact LED bulbs easy with our LED plug and play design. There are no tools required for either the horizontal or vertical configuration, simply switch the bulb in seconds. Our 4-pin LED bulbs are compatible with most CFL ballasts.