This add is for a set of (2) Solid-State Blue LED Lamps you will need for your L4 or L4-B Amplifier Note: I also have Blue LED kits for the 7-Line and 4- Line of RL Drake Radios. Please see my other listings.The Holes that hold the original lamps have to be slightly enlarged to accept the larger diffuser on the LED lamps. Since these lamps will last over 80,000 hours there will be no need to ever change them again!The L4 / L4-B amplifier uses two (2) older style incandescent lamps. These LED lamps, are a direct plug-in for the original L4 / L4-B light bulbs. I also have these Lamps available for the rest of the Drake line of radios, in my other listings and on my web site.