Liquid light guide f/ X-Cite illuminators.  For maximum signal replace every 2-3 years, 4000 hours or 2 lamp changes.  

Direct HAL 100 Replacement:
AxioImager, AxioObserver, AxioExaminer AxioScope A1, Axiovert A1

HAL 100 Replcement requiring external power supply:
All other Axio series microscopes 

All Axio Series

HAL 100, MicroLED Illuminators