The 4D is a great host for high capacity nimh D cells (10Ahr) for those that want to keep “THE CLUB” aspect intact and aren’t ready yet to switch to lithium. Cut down mods take advantage of the higher voltage in lithium cells to make a Mag D shorter and lighter. The range between is almost infinite and the ~50 mm lens/reflector is common enough that there are many different choices available for the number of emitters to run. In The BLF Modding Links Thread you will find many different D mods (especially by member emeritus OldLumens) that should provide some excellent reading.