Welch Allyn Compatible Bulb 03400-U 2.5V Hlogen Bulb for Otoscope, Illuminator Used in the following Instruments: Otoscopes - #24011, #24031, #24020, #24000, #21110 & #21111 Handle Adapter #73550 Illumnators/Transilluminators - #27200, #27250 & #41110 Also Known As: WA03400-U, WA-03400U , WA3400-U , WA3400, 03400-U, 03400U , 3400U , 03400-U